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Leader growth and radial increment on the stem and main lateral roots during three consecutive years following partial girdling treatment were analyzed on 25- to 30-year-old lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.) from a natural stand in west-central Alberta. Simulation of the larval feeding wounds of the weevil, Hylobiuswarreni Wood, consisted of the removal of a 7-mm-wide band of bark from 0% (control), 20%, 40%, 60%, 80%, and 90% of the root-collar circumference of 58 sample trees.Partial girdling reduced leader elongation and radial increment of the leader and lateral roots. Leader height decreased with increased girdling of the root-collar during each of the three post-treatment years. Below the leader, partial girdling of the root-collar did not affect radial increment in the first year, caused an increase during the second year, and a decrease in the third year. At 2 cm above the partial girdles, radial growth above the girdled side of stems was always less than that on the nongirdled side and showed a trend of increase with increased girdling on both girdled and nongirdled sides of the stem. Radial increment was considerably reduced on lateral roots extending below girdle wounds during the three post-treatment years. Two graphs are prepared which can be used to estimate height and radial increment losses in young pine stands infested by H. warreni.

‘Canby’ red raspberry is immune and ‘Latham’ is susceptible to infestation by Amphorophora agathonica Hottes. During a 4-day period, nymphs gained more dry weight and nitrogen on Latham than on Canby. On Latham the dry weight and nitrogen content of honeydew were greater and lO× more total solids and 2× more total nitrogen were ingested than on Canby. Using the volume of honeydew produced per aphid as an index of the quantity of sap ingested, equal or greater volumes of sap were ingested on Canby than Latham. The ingestate from Canby was more dilute than that from Latham. The phloem tissue in petioles of intact Canby leaves was destroyed, but the xylem left intact, by stem girdling. Nymphs on girdled Canby leaves gained as much dry weight as those on normal Latham leaves. Those on the girdled leaves ingested more total solids and more total nitrogen than those on the normal Canby leaves. When girdled Canby leaves were shaded from light, and photosynthesis prevented, nymphs ingested more total nitrogen than those on normal Canby leaves. The levels of total solids ingested from the girdled and shaded and the normal leaves did not differ. On the girdled and shaded Canby leaves the gain in dry weight by the nymphs was intermediate between that on girdled leaves of Canby and normal leaves of Latham, and that on normal leaves of Canby. These results suggest that the immunity of Canby is related to the levels of both solids (largely sugars) and nitrogenous compounds in the ingestate of A. agathonica . It is not known whether this relationship is quantitative and/or qualitative in nature.

Live trapping and tagging methods were employed to assess small mammal populations within two hardwood plantations in southern Ontario. Excessive girdling damage in past years to young planted trees necessitated an evaluation of rodent populations and development of effective control measures. The application of an anticoagulant rodenticide to oat groats bait broadcast over the study area at an ingredient cost of approximately three dollars per acre virtually wiped out the small mammals. Reinvasion from surrounding areas was, however, fairly rapid, particularly during late summer. Further research on longer term control measures using poisoned bait feeder stations is recommended.

The fruit yield of the sexually self-incompatible citrus ‘Ortanique’ can be successfully increased, firstly by the introduction of ‘Valencia’ sweet orange trees for the purpose of cross-pollination, and secondly, by girdling. ‘Valencia’ cross-pollination results in fairly low seed counts in the ‘Ortanique’ fruits, the averages in two successive seasons being 3 and 5 seeds. ‘Minneola tangelo’ is a highly effective pollen source, but induces large numbers of seeds per fruit. The pollen from ‘Tomango’ and ‘Shamouti’ sweet orange is ineffective.

The pathway and distribution of 14C-sugars in flower parts have been examined to find out in which tissue sugars are translocated in the stem of the cut carnation; 14C-sucrose or 14C-glucose was supplied at the base of the cut stem from a feeding solution and the localization and chemical nature of the carbon- 14 recovered from flower parts were investigated. By reducing the rate of transpiration it was found that the uptake of feeding solution was also reduced, but the distribution of absorbed 14C-sucrose in the flower parts was different from that which would be expected if sucrose moved exclusively in the transpiration stream. Autoradiographs demonstrated that 14C absorbed from the feeding solution as 14C-sucrose appeared in both xylem and phloem but predominantly in the latter ; girdling failed to stop the translocation of the absorbed 14C-sucrose. Results of experiments with 14C-sucrose and 14C-glucose showed that sucrose was the mobile sugar and that glucose was converted to sucrose before it was translocated. It was concluded that the translocation of sucrose absorbed from the feeding solution takes place both in xylem and phloem and is regulated by a mechanism involving the loading and translocation of sucrose in the phloem.

Norway spruce stems were artificially weakened by cutting a hole through them. The wood subsequently formed near the discontinuity was observed after six growing seasons following the cutting. Enhanced xylem development persisted in the zone of the discontinuity long after wounding and partial girdling stimuli could be considered to have an effect. This evidence supports the mechanistic hypothesis of stem-form development because mechanical stress level along the stem, originating from wind loading, would be greatest in the region of the discontinuity.

Research was carried out to reduce internal stresses in E. camaldulensis. Altogether, 74 trees of the Circeo National Park were examined; 25 eucalypts were girdled, the cut affecting the entire sapwood, while the remaining trees were taken as controls. They were utilized at different periods after girdling, viz. after 5, 8 and 17 months. The investigations were carried out on butt-logs (up to a height of 3 m) of which diametral boards, 3 m long, were taken, having a thickness proportional to the mean breast height diameter of each tree. The measurements were taken of a total length of 100 in. by a tensodeformometer with an approximation of 0.0001″, determining, together with the length, also the deflection of all the outer strips gradually removed from the board in order to evaluate the strip unit contraction. As concerns board lengthening, the arithmetical difference was determined between the lengths taken before and after the cut. While for unit contractions—expressed by 8 d/l 2 —the values are given in in./sq.in., for unit lengthenings the variations are given in inches. The results obtained must be considered as positive: in fact, deformations were reduced, on the average, to 50 percent. These positive results are accompanied by others, of practical nature, all supporting the effectiveness of the method followed. Mention should be made, in fact, that in sawing logs from control trees diverse cracks occurred very often along the pith, separating diametrical boards almost completely, while no fissure was observed on boards from girdled trees.

Nupserha bicolor postbrunnea Dutt has become established on olitorius jute (Corchorus olitorius), possibly from its wild food-plant, Sesbania aegyptiaca, and from jute it has spread to other agricultural crops. Incidence on the green-manure crop, Sesbania bispinosa, has increased so much in recent years that it has surpassed that on olitorius jute. The stem diameter most favourable for girdling and oviposition in S. bispinosa ranges from 3·1 to 5 mm., whilst in C. olitorius it is from 2·6 to 3 mm. In spite of this wide difference in preferred stem diameter, the ratio of mandibular length to depth of extra-medullary tissue of such stems in the two plants agrees well.All the varieties of capsularis jute (C.capsularis) are unacceptable to the adults though they are acceptable to the larvae. Adults obtained from larvae reared on varieties of capsularis jute also show aversion to capsularis types. The pest selects the susceptible olitorius from amongst capsularis jute when these are grown as a mixed crop. Amongst the olitorius varieties, C.G. is the most susceptible. Plants coming within the height range of 100 to 200 cm. are attacked more than others. Girdling causes suspension of unidirectional vertical growth, and this is followed by the appearance of a number of side branches, which are of little value from the point of view of fibre.

Several papers and many references in other manuscripts have dealt with the relation of growth of the tops and growth of the roots of plants. These generally present data showing the effect of soil types, moisture or mineral elements upon top-root ratio (2, 4, 10). The idea is quite prevalent in some agricultural circles that the relative amount of roots on a plant is determined, if not controlled, by the soil. On the other hand, there are several other factors which can be shown to modify greatly the top-root ratio. Among these are variety, light intensity (10), photoperiod, partial defoliation, girdling, fruiting, and growth substances (14). For example, the amount as well as character of the root system of piece-root grafted apple trees varies with the variety of scion used (5, 9). The type or amount of reserves accumulated in perennial plants as the apple has marked effects upon the subsequent top-root ratio (fig. 1). It has been reported in the literature that plants grown in short days have relatively few roots (1, 11). This conclusion may be strengthened if the plants are not grown to maturity. Also, having few roots in short photoperiods is an effect which may be incidental to the fact that the plants under observation come to flower in short days. Plants which blossom in long photoperiods have been seen to have fewer roots in long photoperiods (6), indicating a correlation between flowering and limited root development. This was found to be the case by Withrow, who used nitrogen supply as a variable with photoperiod (13). She states: "... plants, for the most part, were able to form proportionately larger tops as compared to roots under that photoperiod which brought about flowering as compared to that photoperiod under which the plants remained vegetative. Nitrogen supply did not usually alter the direction of this response, although under either photoperiod there were proportionately larger tops as compared to roots at high nitrogen levels than when the nitrogen supply is limited. ' ' Nitrogen is generally credited with increasing the top-root ratio (2, 4, 10). The data presented in this paper were collected to measure to what extent the ratio of top to root is influenced by some factors in the environment of the top ; also, to see if the relative amount of root formation is consistently related to the function of flowering and fruiting regardless of whether a plant has a greater ratio of roots in short photoperiods, long photoperiods, cool temperatures, warm temperatures or other specific cultural environment.

Studies have shown that Septoria musiva Peck, a North American fungus which occurs commonly as a leaf-spotting parasite on native poplars, produces cankers, in addition to leaf injury, on certain introduced poplars (Populus Rasumowskyana Schneid., P. Petrowskyana Schneid., and P. berolinensis Dipp.), and the native hybrids, Northwest and Saskatchewan poplar.Field observations and inoculation experiments demonstrated that most of the inoculum for spring infection arises from ascospores of a Mycosphaerella stage, and that the fungus enters the stems through mechanical wounds uninjured lenticels, leaf petioles, or stipules. Incipient cankers occur in the bark of the current year's wood, soon girdling leading and side shoots. They later spread from lateral branches into the main stem, developing into perennial cankers which ultimately girdle and kill the trees.

The life history of the white-pine cone beetle, Conophthorus coniperda (Schwarz), was studied in the vicinity of New Haven, Connecticut, in 1958-60. The various life stages and seasonal development are described. The adult female leaves its hibernation place in the litter in April, flies to a developing white-pine cone, and bores into the cone at its junction with the petiole and quickly kills it by girdling. A gallery is bored down the axis of the cone and eggs are deposited in niches along its length. There are 2 larval instars. New adults are present in July. Most adults stay within the infested cones, on the ground, until the following spring.

The disease was first observed at Bear Island, Lake Temagami, Ontario, during the summers of 1930-1931, when it was found on young trees of Populus grandidentata Michx., P. tacamahaca Mill. and P. tremuloides Michx. Later it was found on the same species of poplars in other places in the Temagami Forest Reserve. The affected trees were from three to six years old and usually not over 1.5 inches in diameter.

The larvae of the European pine sawfly, Neodiprion surtifer (Geoffroy), injure their hosts by old-growth defoliation, debarking, and current-shoot girdling. Defoliation is undoubtedly responsible for nearly all the growth loss. Both height growth and radial growth are inversely related to sawfly population levels, but radial growth is affected most, especially at higher population levels. The extent of growth loss is a function of the amount and the rate of foliage removed. Damage after 2 seasons depends upon the quantity of foliage available and removed in both seasons. Trees are seldom without foliage because some new-growth needles appear before all the old-growth needles can be consumed. Even at very heavy population levels defoliation seldom exceeds 90% when old and new foliage are considered together. Since new foliage continues to grow after the sawflies leave the host, the trees “recover” later in the season. Host mortality was not observed even after 3 years of severe defoliation.

When (14)C-sugar and THO were simultaneously introduced through a cut side vein or flap of a squash leaf (Cucurbita melopepo, Bailey cv. torticollis) concurrent translocation of (14)C-sugars, T-photosynthates and THO with parallel, almost flat, gradients was observed in the petiole for periods of 1 to 3 hr. Parallel translocation gradients were not observed when (14)C was introduced as (14)CO(2) and T by painting a leaf with THO. Autoradiography of frozen sections to locate the tissues in which THO was moving was unsuccessful. Steam-girdling blocked the movement of (14)C and T when (14)C-glucose and THO were introduced simultaneously by the flap-feeding technique. If THO moved as liquid water in the phloem along with the (14)C-sugars, as blockage by steam girdling suggests, then solution flow of sugar cannot be excluded as a mechanism of translocation.

1. Flowering clusters of Black Corinth and Thompson Seedless grapes at berry-shatter stage were dipped in GA1 or GA3 at various concentrations. Response to each compound was about equal, as judged by greater berry size in both varieties. 2. GA3 and KGA3 concentrations of 0, 5, 20, or 50 p.p.m. were separately applied to Thompson Seedless at shatter stage by dipping clusters or spraying vines. The compounds were about equally effective in inducing larger berries. 3. In dipping and/or spraying experiments, Black Corinth, Hunisa, and Ohanez showed no greater response to KGA3 and 4-CPA in combination than to either compound applied separately. 4. Carignane clusters at prebloom stage were dipped in KGA3 in the range 0-100 p.p.m. Pollen germinability was markedly decreased by KGA3 at 5-100 p.p.m. and was nil at 100 p.p.m. Treatment with KGA3 at 100 p.p.m. resulted in more berries with a single seed and fewer with three or four seeds. 5. Germinability of pollen obtained from Carignane clusters that had received ...

Four years after establishment, an experiment in regenerating yellow birch (Betula alleghaniensis Britt.) on prepared seedbeds under one-tenth and one-quarter acre circular canopy openings created by cutting and girdling trees in a deteriorated tolerant hardwood stand indicates that all combinations of method and size resulted in satisfactory birch stocking. Yellow birch outgrew its principal competitor sugar maple (Acer saccharum Marsh.), underbrush competition has not jeopardized good birch survival, and deer browsing has been low.En vue d'étudier la régénération du bouleau jaune (Betula alleghaniensis Britt.) sur des lits de germination préparés, des trouées de forme circulaire de 1/10 et 1/4 d'acre ont été pratiquées à l'aide de coupe et annelage dans un peuplement détérioré de feuillus tolérants. Quatre ans après le début de l'expérience le taux de germination du bouleau jaune était jugé satisfaisant pour toutes les combinaisons de méthodes employées et de dimensions des trouées. Le bouleau jaune a surpassé en croissance son principal compétiteur l'érable à sucre (Acer saccharum Marsh.), sa survivance n'a jamais été mise en péril par la competition de la strate arbustive et l'intensité du broutage par le chevreuil a été bas.

A canker disease of cypresses, caused by Monochaetia unicornis, was first observed in Kenya in 1942. Outbreaks appear to have followed a spread from south-east to north-west, the direction of the south-east monsoon, and the disease has now been recorded in nearly all the cypress-growing areas of Kenya, Tanganyika and Uganda, in Southern Rhodesia and the Union of South Africa. The oldest known infections occurred in 1937. The fungus grows in the bark and sapwood, forming cankers which spread rapidly up and down the stem or branch, more slowly round, frequently causing girdling. Cankered trees produce large amounts of resin and a periderm may be initiated in advance of the fungus. Infections occur most commonly at main branch crotches, but cankers also start at the tree collar, on the stem and at minor branch crotches. The fungus exists in nature in three strains having differing levels of virulence, growth rate in culture, size of acervuli and conidia, and retention of viability in conidia. The distribution of one strain appears to be limited by ecological conditions. Acervuli ripen and conidia are liberated from 3 to 8 weeks after the start of the rains. Infections start during the rains and misty weather, the slimy spores being dispersed for short distances only. Conidia may retain their viability for up to 28 months. The local spread of the disease in Kenya has been traced and differing levels of virulence east and west of the Great Rift valley, associated with differences of climate, have been observed. Trees 2 years old are the most susceptible and older trees are only infected in the rapidly growing parts. Cupressus macrocarpa is more susceptible than C. lusitanica, the latter species being heavily infected only where it is growing close to diseased C. tnacrocarpa. Occlusion of cankers occurs in both species but is more effective in halting the spread of the fungus in C. lusitanica. It is suggested that the disease originated from a single focus and may represent the mutation of a strain of Monochaetia unicornis parasitic on cypresses from a strain only parasitic on an indigenous host, Juniperus procera. The fungus may, however, have been imported from abroad.

SUMMARY Patterns of seedshed were studied in several burnt and unburnt stands of Eucalyptus regnans F. Muell. in central Tasmania by catching the seed in traps and examining the capsules on the trees. Timing of the seedshed is important because the bulk of the natural regeneration must normally come from the seed which is shed within one year after burning. In unburnt stands seed was shed throughout the year. During some years the pattern of seedshed was irregular, but after hot, dry summers one-half to three-quarters of the year's seedshed occurred in February-March-April. The capsules themselves were cast off in a less regular pattern; the fallen capsules still contained 16 per cent of the full seed loading. Fire may accelerate seedshed. If the leaves and twigs are scorched, the capsules also are killed and their seed is shed as soon as they dry out; this may take hours or weeks. If the tree is girdled the crown will wilt within days or months, depending on the depth of girdling and the subsequent weath...

Ovipositing females of Nupserha bicolor Thoms, ssp. postbrunnea Breun. cause loss of stem length in jute, Corchorus olitorius, by girdling the stem above and below a slit in which the egg is laid. The slit is made by two successive indentations of the mandibles. It is composed of a central pit and two lateral punctures. Girdling is restricted to that portion of the stem which falls within the stem-diameter range of 0·2 cm. to 0·4 cm.A relationship exists between the length of the mandibles of the female, the depth of the stem tissue from the epidermis down to the periphery of the pith (extra-medullary tissue), and girdling and oviposition.For girdling, the optimum ratio between the mandibular length and the depth of extra-medullary tissue as measured from the epidermal furrow and ridge of the stem (pentagonal in this region) is 1:0·80 and 1:0·99, respectively. Frequency of girdling gradually decreases in those regions of stem where the depth of extra-medullary tissue increases or decreases these ratios.

The effect of 2,4-dinitrophenol (DNP) on sucrose-14C transport in Soya seedlings has been analysed. The aim was to distinguish between an effect of the inhibitor on sugar movement within the phloem sieve tubes themselves, and on the prior steps of uptake and secretion of sugar into the conducting cells. DNP drastically inhibited sucrose-14C transport if it was applied to the 14C-treated leaf immediately before, or during, 14C supply. Transport was also strongly inhibited if DNP was applied along the translocation path while the 14C-treated leaflet was still in position on the plant. When, bowever, DNP was applied through the cut petioles of the primary leaves after removal of the 14C-treated terminal leaflet of the first trifoliate leaf, no inbibition was observed. On the contrary, transport appeared to have been promoted: significantly more 14C disappeared from the upper regions of DNP-treated plants as compared with controls, while in the lower plant parts more 14C accumulated. Different rates of synthesis of sucrose-14C into non-alcohol-soluble compounds could not account for this result. A similar stimulatory effect was observed when DNP was applied to the cut petiole of a primary leaf opposite that treated with 14C. Several indications were obtained that 14C which has reached the lower parts of the plant may circulate upwards again through the phloem within about 15 minutes. When sucrose-14C was introduced into the roots via the xylem, both DNP treatment and prior steam girdling resulted in the apparent accumulation of 14C in the lower plant parts. the results would be compatible with DNP inhibition of upwards movement in the phloem. DNP might also have affected sugar uptake processes in cells neighbouring the translocation path. It is concluded that the inhibitory effect of DNP on downwards phloem transport reported by earlier workers was probably due to an effect on uptake and/or secretion into the sieve tubes, not to an effect on the conducting cells themselves. Modern theories for phloem transport are discussed in the light of these findings.

Treatment of erect stems of Prosopis with near phytotoxic levels of 2,4-D or 2,4,5-T causes the formation of an unusual wood with narrow, thick-walled vessels and axial parenchyma in which cell wall thickening is inhibited. Although reduced in diameter, the vessels formed during 2,4-D and 2,4,5-T treatment are so numerous that there is no significant difference between phenoxyacetic acid and control seedling groups with regard to total area of xylem occupied by vessels. The preferential maturation of xylem vessels over parenchyma and the transformation of fusiform initials into septate parenchyma strands in phenoxyacetic acidtreated Prosopis resemble the structural changes reported to occur after girdling in the cambial tissue of other arborescent angiosperms. Bending experiments indicate that tension-wood fibers of Prosopis differentiate in response to an auxin deficiency. However, xylogenesis in erect stems treated with TIBA is affected such that a significantly higher proportion of the cambial cell population becomes axial xylem parenchyma. MANY WELL-DOCUMENTED attempts have been made to account for the killing actions of 2,4dichlorophenoxyacetic acid and the other phenoxyacetic acids since the advent of their utilization. Early explanations cited the disruption of the phloem or the depletion of stored carbohydrates (Tukey, Hamner, and Imhofe, 1946; Loustalot and Muzik, 1953). However, as further explanations were sought, it became apparent that many factors earlier attributed to causing death of the plants represented only part of the total action of the phenoxyacetic acid herbicides. Recent investigations have shown that many aspects of plant development, including cell expansion and proliferation, are affected by herbicides (Kiermayer, 1964). Cardenas et al. (1968) report that 2,4-D causes an abnormal increase in axis growth at the expense of other organs, especially leaves and young roots. Picloram has been shown to alter sink activities such that there is preferential movement of assimilates to the more mature parts of the plant axis (Leonard, Glenn, and Bayer, 1972) at the expense of young leaves (Sharma and Vanden Born, 1971). In seedlings of Pinus resinosa treated with picloram or 2,4-D both root growth and needle extension are inhibited, but tissue proliferation in the stem, hypocotyl and upper root is promoted (Wu et al., 1971). Abnormal axis growth following 2,4-D treatment is associated with high levels of aberrant 1 Received for publication 17 November 1972. We thank Elsie D. Morey for valuable technical assistance and Dr. William R. Atchley for help with the statistical analysis. This work was supported by the Noxious Brush and Weed Control Program and the Institute for University Research of Texas Tech University. nucleic acid and protein synthesis (Cardenas et al., 1968), and, as might be expected, a wide variety of anatomical modifications accompany these physiological changes. In general, the least differentiated tissues of the axis are most subject to proliferative activity following herbicide treatment. Proliferation of cambial, phloem, cortical and other tissues may result in tumor formation (Murray and Whiting, 1947) in which the cells may follow a number of developmental pathways, including differentiation as tracheary elements or organization into root primordia. In some tissues 2,4-D may affect cell differentiation by inhibiting cell wall synthesis (Bourke, Butts, and Fang, 1962). The study reported here on Prosopis, though limited to effects on wood formation, attempts to further explain the killing action of the phenoxyacetic acid herbicides and, more importantly, to expand the work in this area on woody plants. In addition it was realized early in this study that normal wood formation in Prosopis was in itself of considerable interest. For example, xylem parenchyma may comprise up to 75 % of the axial system of cells, and the fiber component, even in erect stems, is largely of the tension-wood type. The experimental studies on Prosopis reported herein reveal information on the mechanisms controlling cell differentiation of those xylem elements not easily accessible to study in other systems. MATERIALS AND METHODS-2,3,5-triiodobenzoic acid (TIBA) and 2,4-dichlorophenoxyacetic acid (2,4-D) in anhydrous lanolin (2.0 %, w/w) were applied in a ring around the midpoint of the first or third internode of erect fourto six-week

The Arizona five-spined engraver, Ips lecontei Swaine, attacked ponderosa pine trees poisoned with a fast-acting silvicide containing cacodylic acid (dimethy]arsenic acid). The density of attack and subsequent mortality of the brood and attacking adults varied considerably with the time of year the trees were poisoned. August-treated trees attracted the greatest density of attacks, and the rate of beetle mortality was higher than in trees poisoned at any other time of the year.

A sampling technique is described for estimating the abundance of the weevil, Hylobius warreni Wood, in even-aged lodgepole pine stands. The percentage of trees currently infested is the basic measurement sought in the survey of a stand. Estimates of growth reduction (radial increment of stem, length of leader shoot) are given for young pine trees with 50% girdling damage. The relation between minimum weevil population level required to achieve 50% girdling and stand age class is described. This relation serves to establish a basis for gauging the severity of infestation.

Growing navel orange fruits (Citrus sinensis) 5.4 to 5.7 centimeters in diameter were used as a model system to determine the effects of transpiration and carbohydrate translocation on water and osmotic potentials in fruit tissues. Evidence supported the hypothesis that osmotic potential in the vesicles would be affected little by changes in transpiration or carbohydrate translocation because the vesicles are anatomically isolated from the transpiration stream and are at the end of the carbohydrate translocation pathway. In the mesocarp tissue, which contains a vascular network, osmotic potential decreased during the daytime when environmental conditions favored transpiration and increased at night. Exocarp water potential followed a similar pattern. Girdling of the stem above the fruits 5 days before sampling caused an increase of osmotic potential in the mesocarp but had no effect on exocarp water potential. Neither diurnal changes in transpiration nor girdling of the stem affected the osmotic potential of the vesicles.Osmotic potentials in all tissues of the fruit were in the range of -10 to -15 bars. Measurements of osmotic potential at 16 locations along a longitudinal plant through the fruit axis showed that osmotic potential increased from the stem to the stylar end, but it decreased from the pericarp tissues to the vesicles. As exocarp water potential decreased during a 20-day period after watering, osmotic potential decreased in the vesicles and exocarp. Turgor pressure, calculated as the difference between water and osmotic potentials, decreased with water potential in the vesicles but not in the exocarp. The lack of decrease of turgor pressure in the exocarp may result from a measurement error caused by pectins or from osmotic adjustment related to carbohydrate accumulation at low water potentials.

Experiments were performed in 1958 on three seedless varieties of Vitis vinifera to determine their responses to gibberellin. Berry-growth curves of Black Corinth and Thompson Seedless were double sigmoid when growth increments in diameter were plotted. Gibberellin increased berry diameter but did not alter the general shape of the curves. On clusters of Black Corinth or Thompson Seedless, only the treated portions responded to gibberellin. In Black Corinth, increasing concentrations from 1 to 100 ppm of gibberellin usually progressively increased berry size and length-to-width ratio. Black Corinth showed little increase in size of berry as a result of compound absorbed by leaves. The percentage increase in length of young Thompson Seedless clusters dipped in gibberellin was greatest in the apical portion and least in the basal (peduncle). Thompson Seedless vines were sprayed with gibberellin at 10, 25, or 50 ppm, at four prebloom stages. Length of cluster was increased by the second application. Weight of fruit was sometimes decreased by gibberellin, but in two of four instances in which crop level could be eliminated as a factor, maturation was hastened. Gibberellin at 1 ppm and higher, applied after shatter, increased berry size of Thompson Seedless. The compound at 1,000 ppm injured the berries, but not the foliage and shoots. Largest berries resulted from combined gibberellin and girdling. The largest berries in Thompson Seedless were produced by spraying at the shatter stage; later sprayings produced progressively smaller berries. Gibberellin absorbed by leaves had only a small effect on enlargement of fruit. Gibberellin increased berry size of Black Monukka.

Introduction 255 Formation of grafts .... . . . . . . . . . . . . . . . . . . . . . . 256 Types of grafts 258 Self-grafting 258 Intraspecific grafting 258 Interspecific grafting 260 Living stumps .. ........ 260 Prevalence of root-grafting 263 Implications 264 Ecology 264 Stand development 264 Response to thinning. 266 Forest Management 268 Pathology .... . . . . . . . . . . . . . . . . . . . . .. 268 Resistance to windthrow 270 Girdling 270 Silvicides 270 Nest plantings 273 Summary ... 274

The roles of auxin and nutrition in determining the expression of dominance within a whorl of current shoots were investigated. It was demonstrated that the removal of shoots from a whorl induces compensatory growth in the remaining shoots. Treatments that block auxin movement (triiodobenzoic acid (TIBA), girdling) or decrease auxin production (defoliation, decapitation) also induce compensatory growth, at the same time inhibiting growth in the treated shoot. On the other hand, capping a decapitated and defoliated shoot with indoleacetic acid (IAA) in lanolin maintains diameter growth in the shoot stump and prevents the occurrence of compensatory growth. It is concluded that the shoots in a whorl compete for dominance by competing for a common supply of nutrients transported from the preceding internode. The quantity of nutrients diverted into a shoot, hence growth, is a function of the shoot's capacity to produce growth substances. Hormone synthesis, as well as shoot length, fascicle number, and number of buds in the current whorl are predetermined in the winter bud.The degree of dominance, expressed as the ratio of the sizes of the terminal and the longest lateral in the whorl, depends on the nutrient supply available during the period of winter bud development as well as during the period of shoot expansion.

A 4-year evaluation showed that Conophthorus ponderosae Hopkins destroyed an average of 24.8% of the potential ponderosa pine seed crop in New Mexico. Adults emerged from the cone in which they developed from 25 April to 20 May and immediately attacked developing, 2nd-year ponderosa pine cones. The female killed the cone by girdling the axis, then constructed a gallery along one side of the axis. One female attacked a maximum of 4 cones in cage tests. Only 1 female attacked a cone and was normally accompanied by a male. An average of 6.7 eggs was laid in each cone. The eggs hatched 5–6 days after oviposition under field conditions. There were 2 larval instars. Pupation occurred as early as 13 days after oviposition, and callow adults were found as early as 24 days after the cone was attacked. The beetles overwintered as adults and emerged in peak numbers from 5 to 20 May the following spring.

SUMMARY Serious local and seasonal damage to exotic pine plantations is being caused by possums of two species, the black-tailed wallaby, and the allied rat. These animals attack the trees to obtain food material in the combial layer. Damage consists of bark stripping and girdling or partial girdling. Severe damage results in the death of the tree. Recovery may take place after less severe damage but the tree becomes deformed and its value as timber is substantially reduced. Several factors are involved, of which the most important are availability of ground cover and food material. The presence of the former makes the forest a suitable habitat for small mammals, and limitations on the latter cause them to attack the trees in times of food shortage. Proximity of native vegetation and water is also important as the mammals tend to harbour in such areas. Removal of cover would reduce the damage. Adjustment of the habitat is preferable to destruction of the animals. If this proves ineffective, the offending ...

1. Clusters and foliage of Black Corinth grapes were sprayed with 4-chlorophenoxyacetic acid at concentrations of 10, 25, 50, 100, or 300 p.p.m. Large berries and compact clusters developed when the acid was applied in the range from 10 to 50 p.p.m. Dipping of clusters gave similar results. 2. Parts of Black Corinth vines were sprayed with 4-chlorophenoxyacetic acid at 25 p.p.m. on May 24, May 28, June 3, June 7, or on June 14. June 3 was apparently the earliest time to spray in 1951 to obtain compact clusters with almost no hard seeds. Dipping of clusters gave approximately the same results. 3. Dip applications of 4-chlorophenoxyacetic acid at 50 p.p.m. to Black Corinth clusters resulted in berries as large as those produced after both girdling and application of growth-regulator. 4. Only the parts of clusters of Black Corinth grapes treated with growth-regulator usually developed large berries and thickened pedicels. The compound, or stimulus induced by it, apparently failed to move from the treated are...

Summary Spiral grain in radiata pine (Pinus radiata D. Don) is mainly a defect of corewood and is seldom strongly developed in wood occurring more than 10 growth layers from the pith. Development of spirality in this species can be explained in terms of spiral flow of metabolites induced by the phyllotaxy of the vascular supplies to short shoots (the “needle traces”). Experiments are described in which spiral girdling and similar techniques are used to change the orientation of newly formed xylem elements so that they are in alignment with the altered direction in which metabolites and growth substances flow. By these means grain angles as large as 45° to the stem axis have been produced within one season's growth. Lesser but highly significant changes of grain angle have been brought about by modifying the dimensions and phyllotactic patterns of needle traces. The experimental trees have provided outstanding material for studying the anatomical bases of these changes which indicate an extremely plastic r...

1. BfiNNING, E. 1931. Untersuchungen fiber die autonomen tagesperiodischen Bewegungen der Primarblatter von Phaseolus multiflorus. Jahrb. wiss. Bot. 75: 439-480. 2. GARNER, W. W. and H. A. ALLARD 1931. Effect of abnormally long and short alterations of light and darkness on growth and development of plants. Jour. Agr. Res. 42: 629-651. 3. GRIESEL, W. 0. and J. B. BIALE 1958. Respiratory trends in perianth segments of Magnolia grandiflora. Amer. Jour. Bot. 45: 660-663. 4. HIGHKIN, H. R. and J. B. HANSON 1954. Possible interaction between light-dark cycles and endogenous daily rhythms on the growth of tomato plants. Plant Physiol. 29: 301-302. 5. HILLMAN, W. S. 1956. Injury of tomato plants by continuous light and unfavorable photoperiodic cycles. Amer. Jour. Bot. 43: 89-96. 6. NANDA, K. K. and K. C. HAMNER 1959. The effect of temperature, auxins, antiauxins, and some other chemicals on the endogenous rhythm affecting photoperiodic response of Biloxi soybean (Glycine max. L.; Merr.). Planta 53: 53-68. 7. RICHTER, G. and A. PIRSON 1957. Enzyme von Hydrodictyon und ihre Beeinflussung durch Beleuchtungsperiodik. Flora 144: 562-597. 8. VERKERK, K. 1955. Temperature, light, and the tomato. Mededel. Landbouwhogeschool Wageningen 55: 176-224. 9. WENT, F. W. 1957. The Experimental Control of Plant Growth. Chronica Botanica Co., Waltham.

Baris granulipennis (Tourn.), originally described from Egypt, has become a serious pest of water-melons (Colocynthis citrullus) in Israel, where hitherto its presence has not been recorded, and has been found on melons and cucumbers, but not on vegetable marrow or squash. Economically serious damage results from girdling of the stem end of the fruit by the female, prior to oviposition.The incubation period of the egg, on average, is 3·7 days at 30° and 6 days at 22°C. The larvae feed on developing seeds inside the fruit and pupate there. The total development period occupied from 25 to 42 days in the summer, when the temperature fluctuated between 24 and 29°C. The cocoon is made by glueing minute pellets together. These consist of dried pulp from the fruit mixed with a secretion which is ‘milked’ from the anus, and is believed to be produced in the Malpighian tubules. The preoviposition period is about four days, and the length of adult life is several weeks. There are three generations a year, and four if weather permits. Adults overwinter in hibernation. It is suggested that the increase of cucurbit cultivation, and the lengthening, by irrigation, of the cropping period, may have permitted an increase in the weevil population to pest proportions.

The large genus Phoradendron includes not only species like those of North America already described and Ph. fanshawei from Trinidad, with cortical strands and sinkers comparable especially with those of Viscum capense , but also others with very different modes of attachment. Some have much enlarged primary haustoria, with subordinate cortical strands and sinkers ( Phoradendron trinervium on some hosts) or without them ( Ph. hartii, Ph. flavens ). Ph. trinervium on Calophyllum lucidum , in contrast with its behaviour on other hosts, forms no major wedge but the cortical strands show an exaggerated development with anastomosis of the strands and the formation of numerous sinkers. In Phoradendron crassifolium and Ph. tetrapteron the haustorium simply spreads against the host wood to form a saddle-like attachment. In Ph. perrottetii also the haustorium spreads against the host wood, occasionally girdling it completely, forming downward branches, sometimes twenty or more, which run parallel and in their older parts fuse. Dendrophthora inaequidentata forms a very large primary haustorium, with slender cortical strands. The growth of the haustorium in width is accompanied by conspicuous hypertrophy of host wood on the lower side of it, the vessels and other elements of which abut on the haustorium, linking up with the parasite vascular system and without continuity with host wood above the haustorium. Tangential enlargement of the haustorium with stimulation of the adjoining cambium and annexation of the wood it forms occurs also though less conspicuously in some species of Phoradendron , particularly Phoradendron trinervium (on Rollinia mucosa ) and Ph. flavens .

In aspen, wounds exposing the xylem to the atmosphere result in pigment production around the wound. Experiments were conducted to help clarify the early origins of this wound-initiated discoloration. Browning began within 7 days after wounding of tissues and spread vertically. The early pigments are probably phenolic compounds produced in the xylem parenchyma from stored lipids. Production of early pigments involves stepwise degeneration of the cell nucleus and cytoplasm. High concentrations of antimicrobial agents applied to fresh wounds increased the rate of pigmentation. Phloem girdling had no effect on pigment formation. Xylem did not discolor if killed without exposure to the atmosphere. These early pigments may be related to the dark pigments found in most aspen trees.

An experiment was set up to evaluate the effect of three techniques on the flowering of four varieties of Irish potatoes commonly grown in Louisiana. Records were taken in regard to the production of flower clusters and open flowers. As averages of the four varieties, flowering was highly stimulated by the wire girdling and stem incision treatments. The pruning of stolons had no significant effect on flowering. None of the treatments had a significant effect on the flowering of the sparsely blooming varieties, Triumph and Red LaSoda. The flowering of both Sebago and Katahdin was greatly increased by wire girdling; meanwhile the maximum increase in flowering of Sebago was obtained through stem incision.

Young Douglas fir in British Columbia sustained damage from Phomopsis lokoyae Hahn during the winter of 1948–49. Damage in the form of annual stem and branch cankers, leader die-back, and stem girdling was confined to trees, or parts of trees, 4 in. in diameter or less. Fungus activity was confined to Douglas fir bark and cambium tissues for the single dormant season. Outbreaks of the fungus are recurrent in British Columbia, reaching epidemic proportions only at irregular intervals.

B. COMPARATIVE STUDY OF GRAFTED AND NONGRAFTED SUPPRESSED TREES .... ...... 8 Methods and Results .... 8 Bark girdling experiments .... ...... 8 Height and diameter growth ....... . 11 Missing rings 12 Living snags 13 Discussion .. .. .. ... ... ... ... 13 III. ANATOMY OF GRAFTS . .. 15 A. OBSERVATIONS ON THE STRUCTURE OF GRAFTS 15 B. HYPOTHESIS OF GRAFT FORMATION ... . 16 C. IMPLICATIONS OF GRAFT STRUCTURE, FOR WATER TRANSPORT BETWEEN GRAFTED TREES 17

Increasing numbers of trees of Pacific dogwood, Cornus Nuttallii Aud. and madrona, Arbutus Menziesii Pursh., infected with a pathogen which causes serious cankers on the stems, ultimately girdling ...

The contents of starch, total sugar, crude fat, and moisture were determined during the spring (late March until mid-June) in needles, bark, and wood of 1-year-old balsam fir shoots variously shaded, defoliated, and girdled in late March. The starch content in control shoots peaked during the first week in June, about the time vigorous current shoot elongation began. Shading reduced the concentrations of both starch and total sugar throughout the experimental period, while defoliation decreased them after about mid-spring. Girdling increased the carbohydrate content during early spring in both shaded and unshaded shoots, but decreased it in defoliated shoots. It is concluded that the bulk of the starch accumulating in conifers during the spring is derived from current photosynthesis, the rest being regenerated from carbohydrates produced during the previous year and stored overwinter. Timing the lifting date to maximize the springtime accumulation of starch might be an important consideration when transplanting conifer seedlings.

An extensive dieback and canker disease of chestnut oak (Quercus prinus L.) in Pennsylvania was proved to be caused by Botryodiplodia sp. Isolations from infected stems, branches, buds, and petioles, many of which displayed stromata of Botryodiplodia sp., yielded cultures of this fungus. Inoculations of chestnut oak seedlings and saplings with Botryodiplodia sp. induced symptoms identical with those observed in nature. The fungus was subsequently reisolated from the inoculated diseased tissues. Symptoms occurring in nature were foliar blight, branch dieback, and branch canker. Extensive foliar symptoms, which appeared in late spring and early summer, probably resulted from infections which took place late in the previous summer or fall. Frequent association of a scale insect, Asterolecanium sp., with the disease implicated it as a contributing factor in the disease cycle. Maximum radial growth of the fungus on cornmeal and Bacto yeast nitrogen base agar occurred at 20 and 25 °C, respectively. Light was necessary for the production of stromata and conidia in culture. Microtome sections of petri dish cultures and diseased twigs showed that the fruiting structures of the pathogen were uni- or multi-locule pycnidial stromata. The stromata averaged 400–500 μ. in cross section and contained conidia which at maturity were brown, one-septate, and measured 13 × 27 μ.

Pinus strobus L. trees were grown on a clinostat. Although elongating shoots moved in almost the reverse of the normal pattern, they reached a normal original angle. Compression wood (CW) formed only on the upper side of branches opposite where CW had previously formed. Neither treatments to remove epinasty (girdling branches, removing leaders and branches), nor treatments to bend branches out of position changed CW distribution. On trees grown off the clinostat, branches bending upwards after removal of the terminal formed CW on the upper side before reaching vertical. Main stems could form CW on the upper side after having been tipped to induce CW formation on the under side. It is suggested that epinasty is not involved in either early shoot movements or in compression wood location and that when gravity stimulates CW formation on the under side of a shoot it preconditions the upper side for CW formation, thus establishing an equilibrium position for the shoot.

Tillandsia usneoides, popularly called "long moss," "black moss," or " Spanish moss," is the most widely distributed representative of the tropical and subtropical family Bromeliaceae. According to SCHIMPER (I) it extends from southern Virginia, its northern limit, as far southward as the Argentine Confederation. It forms everywhere a conspicuous and characteristic object of the landscape, its long gray festoons adorning not only trees of the virgin forest but many cultivated ones as well. Although the beauty of the landscape is enhanced by its presence, its growth upon ornamental trees is regarded often with apprehension, a common impression being that it lives parasitically. A most casual examination, however, will reveal the fact that the moss is in no way connected with the tree, but merely wraps its dead, wiry stems loosely around the twigs in order to support itself. Old festoons which have hung in the same place for years occasionally show a connection with the bark, the annual growths of the limb finally enclosing some of the decorticated moss stems; much in the same way that an old horseshoe hung astride a branch and left unmoved for a long time will be partially enclosed. An indirect cause of the popular belief in the parasitism of Tillandsia is its preference for sunny exposures. This habit would tend to keep it from trees having a dense shade. In dark forests it hangs suspended from the higher limbs of tall trees, especially those that are dead. Many a cultivated tree when in perfectly healthy condition possesses too dense foliage to serve as a host for Tillandsia, but if for some reason the supply of leaves should be reduced, the light conditions might be such as to make the presence of the epiphyte possible. Should it make its appearance, the owner of the tree would be very apt to regard the moss as the cause rather than the result of the reduced foliage. A proof of the true epiphytism of the plant is its longcontinued and vigorous growth upon decorticated limbs of dead trees. Near Baton Rouge are many such trees, killed by girdling long ago

The phenotypic responses of suppressed trees were studied in a 60—year—old white pine stand. The first evidence of suppression is a tree—wide decrease in the production of secondary xylem. Height growth is relatively insensitive. During the latter 30 years of life suppressed trees made 50.7% of their total height growth but only 19.1% of their total diameter growth. Eventually the cambium fails to cut off xylem at the base of the tree. With time, the sheath of new—formed xylem retreats from the based giving rise to an increasingly large zone of missing rings. Girdling experiments indicate that diminished supplies of food and growth regulators move through the zone of missing rings to support primary root growth. Apparently the phloem remains functional in the zone of missing rings. Either the phloem can function for periods greater than 1 or 2 years, or the cambium cuts off phloem alone in the missing ring zone. In the normal cambial cycle, phloem alone is produced during the last part of the growing seas...

Adults and eggs of Brachyrhinus sulcatus (F.) were introduced into screened cages containing Concord grape plants. Eleven adults per cage produced complete defoliation and nearly complete fruit loss in the first season. The threshold of economic loss was 1–3 adults per plant per season. An index was developed for estimating root injury caused by larval feeding. Larvae fed first on phloem tissue producing girdled roots. The xylem was intact except in cases of severe injury. Vigor and fruitfulness over a 3-year period were not significantly affected by root injury.