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BELL, DAVID T. (Department of Botany, The University of Western Australia, Nedlands, W.A. 6907, Australia). Eighteen years of change in an Illinois streamside deciduous forest. J. Torrey Bot. Soc. 124:174-188. 1997. The vegetation structure of the streamside forest along Hickory Creek in northeastern Illinois was recorded five times during the period 1977 to 1995. In 1977, lowland parts of the forest subject to frequent flooding were dominated by Fraxinus pennsylvanica, Crataegus mollis and Ulmus americana, gradually progressing vertically to an unflooded upland forest dominated by Quercus rubra, Crataegus mollis and Acer saccharum. Over the 18 years of recording, the lowland, flooded section of the forest showed replacement of Crataegus mollis by Ulmus americana. In the unflooded upland, Crataegus mollis was generally replaced by Acer saccharum. Mean tree diameter growth over the period was 2.78 mm yr-' and mortality 3.10% yr-'. In general species with low rates of growth had high rates of mortality. Of the more common species, annual rates of mortality in Crataegus mollis, Fraxinus pennsylvanica, Ulmus americana and Acer saccharum were 7.0, 3.3, 1.8 and 0.5, respectively. Total tree (

On 6 December 1994 a severe ice storm hit several midwestern states. We inventoried damage and woody debris input from the storm in 30 0.1-ha permanent plots in an old-growth oak-hickory forest in northern Missouri. Twenty-seven percent of 1386 live trees 22 cm dbh were damaged but only 7% were severely damaged. Basswood (Tilia americana) and American elm (Ulmus americana) were the most susceptible species; white oak (Quercus alba), eastern hophornbeam (Ostrya virginiana) and shagbark hickory (Carya ovata) were among the least susceptible. Damage levels increased with stem diameter, and trees occupying dominant crown positions were more heavily damaged than suppressed trees. Damage severity was highly variable across the landscape, but trees on lower slopes and mesic aspects tended to have more damage, even for a given species. Coarse woody debris input from the storm averaged 5.1 m3/ha, 27% of the prestorm volume, with northern red oak (Q. rubra) and white oak contributing 79% of the total. This single event will probably have minimal impact on stand composition and structure, but repeated ice storms at 20-yr intervals likely influence forest dynamics in midwest oak-hickory forests.

BRUCE, K. B., G. N. CAMERON (Department of Biology, University of Houston, Houston, Texas 77204) AND P. A. HARCOMBE (Department of Ecology and Evolutionary Biology, Rice University, Houston, Texas 77251). Initiation of a new woodland type on the Texas Coastal Prairie by the Chinese tallow tree (Sapium sebiferum (L.) Roxb.). Bull. Torrey Bot. Club 122:215-225. 1995.-The chronosequence method (stand ages 0-20 years) was used to study the invasion of the Upper Coastal Prairie of Texas by the Chinese tallow tree and to learn whether this exotic plant would be replaced by native woodland species. This invasion marked a dramatic transformation of community structure. Dominance of life forms shifted rapidly (< 10 years to canopy closure) as graminoids and forbs were replaced by trees and shrubs during succession. Size-frequency distributions of the trees showed that stands were not even-aged. Many stands in the oldest three age classes exhibited descending monotonic tree size distributions. Because Chinese tallow produces seeds soon after establishment, it seems likely that the rapid increase in density was the result of initial trees acting as seed sources. The most common native trees that appeared in the survey were generally small-seeded inhabitants of local riparian areas, e.g., hackberry (Celtis laevigata), elm (Ulmus americana), green ash (Fraxinus pensylvanica), and yaupon (Ilex vomitoria). Low densities of these species indicated slow invasion rates compared to that of tallow. Currently, stands are virtually monospecific. However, the non-tallow species showed a significant increase in density with stand age which suggests that these woodlands may become more diverse in the future.

Site-index curves for evaluating the growth potential of American elm in native timber stands in Kansas were developed from data gathered in the 1964-1965 Kansas forest inventory. American elm (Ulmus americana L.) is the most common native elm found in Kansas. The wood is used principally for agricultural implements, barrels, furniture, and pallets (Stephens, 1969). It grows best on better drained, rich bottomland soils, and in the western portion of its range, it occurs along watercourses with boxelder, green ash, and cottonwood (Harlow and Harrar, 1950). American elm can be found on nearly all soil types within its range (Fowells, 1965). It ranks third in total standing biomass in Kansas and is harvested extensively, but experiences very high natural mortality from Dutch elm disease (Raile and Spencer, 1984). Evaluation of site productivity (wood-producing potential of an area) is an important aspect of management for attaining maximum benefits from forest lands. The site-index method is the most widely accepted means for determining site quality. It uses tree height/age relationships, which correlate well with timber yields. By definition, site index is the average height at age 50 years of dominant/codominant (overstory) trees in a fully stocked, evenaged stand. Curves or tables have been published for many commercial tree species in the United States (Carmean et al., 1989). Site quality is best determined by local site index curves. In Kansas, only curves for black walnut (Juglans nigra L.), hackberry (Celtis occidentalis L.), and green ash (Fraxinus pennsylvanica L.) have been published (Geyer and Lynch, 1987; Lynch and Geyer, 1988; and Geyer and Lynch, 1990, respectively). The purpose of this paper is to provide another in a series of site-index equations, curves, and height tables for important tree species growing in natural stands in Kansas.

HUENNEKE, L. F. (Ecology & Systematics, Cornell University, Ithaca, N.Y. 14853). Understory response to gaps caused by the death of Ulmus americana in central New York. Bull. Torrey Bot. Club 110: 170-175. 1983.-Circular plots of 250 m2 area centered on standing dead stems of Ulmus americana were used to sample understory vegetation in canopy gaps created by the death of elms. A total of 37 plots were sampled in 28 sites representing a variety of wetland habitats. Shrub species typical of open habitats were abundant in gaps created by the death of 2 or more neighboring elms (multiple-tree gaps) but not in single-tree gaps. Multipletree gaps contained fewer seedlings and saplings of canopy tree species than did single-tree gaps. The patchiness of occurrence of the open-canopy shrubs and their relationship to multiple-tree gaps were not reflected in conventional large-scale (0.1 ha) vegetation samples of the same stands. The establishment of dense patches of shrubs may inhibit tree regeneration within the multiple-tree gaps.

On trees in bottomland forests near Winnipeg, Manitoba domi- nated by Ulmus americana, Fraxinus pennsylvanica, and to a lesser extent Acer negundo, Leskea obscura/polycarpa was the dominant bryophyte, with Anomodon minor, Frullania inflata, and Orthotrichum pumilum sometimes also prominent. On trees in the upland Populus tremuloides-Quercus macro- carpa forests in the same area, Amblystegium juratzkanum, A. varium, Brachy- thecium salebrosum, Mnium cuspidatum, and Pylaisiella polyantha were domi- nants. The bryophytes prominent in bottomland forests are eastern boreal while the upland dominants, except Pylaisiella polyantha, which is boreal, are pan-North American. We suggest that the river valleys provide favourable ecological niches, especially regarding higher humidity levels, and allow the westward extension of predominantly eastern bryophytes while excluding by spring flooding the pan-North American species.

DUNN, C. P. (Savannah River Ecol. Lab., Drawer E, Aiken, SC 29801). Shrub layer response to death of Ulmus americana in southeastern Wisconsin lowland forests. Bull. Torrey Bot. Club 113:142-148. 1986.-The relationship of the shrub layer to soil factors (K, pH, P, Mg) and to death of canopy elms was studied on a stand basis in 15 southern Wisconsin lowland forests. Ordination and correlation analysis revealed a positive relationship of shrub layer species composition to soil K, but not to pH, P, or Mg. Rank correlation of species composition to density of dead elm was not significant. Total shrub density, however, did show a relationship to dead elm density. When dead elm density was greater than 5 stems/ha, shrub density increased significantly and predictably. If the density of dead elm/ha is lower than this critical density, no community (i.e., whole stand) response can be detected and shrub response is essentially a small gap phenomenon. Above this critical density, shrub density increases significantly as the number of dead elms increases, resulting in a transition from small gap processes to a more general openness. That is, as the number of dead trees/ha increases, the gap effect widens and gaps begin to coalesce.

ment Station. This study supported by The Kansas Agricultural Experiment Station, also fulfilled a part of the requirement of the Ph.D. degree in plant ecology. ABSTRACT. On the Republican River floodplain in Clay County, Kansas, 39 forest stands were plot sampled in 1968. Salix interior (sandbar willow), S. amyg- daloides (almondleaf willow), and Populus deltoides (cottonwood) appeared the first or second year after alluvium was exposed above water level. Salix interior rarely persisted more than 10 years, S. amygdaloides not more than 30 years, and P. deltoides about a century. Young of these species did not survive in established stands. After about 100 years dominant trees included Ulmus americana (American elm), Celtis occidentalis (common hackberry), Fraxinus pensylvanica (green ash), Morus rubra (red mulberry), and Acer negundo (boxelder). No stand had attained climax, but Celtis occidentalis and Ulmus americana would likely have been dominants. Celtis may be the sole dominant in the future now that Dutch elm disease has en- tered the area. For young (0-10) and old (>60 years stands, mean tree density was 24,000/ha (9,710/acre) and 5,000/ha (2,020/acre), mean basal area was 20 m2/ha (87 ft2/ acre) and 39 m2/ha (170 ft2/acre) and mean basal area per tree > 6 cm diameter was 58 and 638 cm2, respectively. The amount of light that penetrated the forest capony ranged from 18% in young to 2% in old stands. Competition, especially ef- fects of shading, is thought to be more important than changes in soil in eliminating pioneer woody species. Polygonum lapathifolium, Ambrosia trifida and Conyza canadensis were the most common herbs in young stands. Galium aparine had a frequency of 20% in young stands and over 70% in stands more than 30 years old. Rhus radicans and Partheno- cissus quinquifolia were absent in young but common in old stands. Studies of floodplain forest succession provide knowledge that can be applied in managing timber, wildlife, recreation, and floods. Such forests in Kansas and nearby states have been little studied. In Kansas Schaffner (1906) referred briefly to river-bottom forests in Clay County; Smith (1940) to one 200-year old stand in the Smoky Hill Valley in Geary County; and Gesink, Tomanek and Hulett (1970)

The Oglala Sioux Indians in southwest South Dakota instituted in 1970 a range management program involving the production of native game animals for recreation fee hunting. They have two forest-parkland pastures of about 4,000 acres each. These pastures are enclosed by game fences of heavy woven wire, 7.5 feet high. This paper is concerned with these two pastures, referred to as the game range. The Indians also have a 20,000-acre badlands pasture enclosed by natural barriers and a heavy barbed-wire cattle fence. The game range is a land of rugged topography located near Allen, S. Dak. Its plant cover includes ponderosa pine (Pin us po nderosa) forests, open parklands, and savannahs. The steep-sided drainages have good stands of deciduous trees, including bur oak (Quercus macrocarpa), green ash (Fraxinus pennsylvanica), and American elm (Ulmus americana), and deciduous shrubs including

BOERNER, R. E. J. AND Do-SOON CHO (Dept. Bot., Ohio State Univ., 1735 Neil Ave., Columbus, OH 43210). Structure and composition of Goll Woods, an old-growth forest remnant in northwestern Ohio. Bull. Torrey Bot. Club 114:173-179. 1987.-Species composition, sizefrequency distributions, and environment-vegetation relationships were studied in Goll Woods, the last known uncut remnant of the Black Swamp forest of northwestern Ohio. Relatively well-drained fossil beach ridges were dominated by sugar maple (Acer saccharum) and beech (Fagus grandifolia), with sycamore (Platanus occidentalis) and white oak (Quercus alba) also common; poorly drained flats were occupied by silver maple (A. saccharinum), American elm (Ulmus americana), bur oak (Q. macrocarpa), and ashes (Fraxinus spp.). Transitional sites had higher abundances of basswood (Tilia americana), ironwood (Carpinus caroliniana), red oak (Q. borealis), and red maple (A. rubrum). Regressions of axis scores from Detrended Correspondence Analysis indicated relationships among species composition and soil texture. Bur oak, white oak, sycamore, chinquapin oak (Q. muehlenbergii), and cottonwood (Populus deltoides) had emergent individuals over 1 m dbh but lacked stems 300 yr ago.

Mortalite d'U.a. depuis 1926 et influence sur les modifications de la composition specifique, mortalite due a la graphiose

The natural replacement of trees killed by the Dutch elm disease was studied in four forest types in southeastern Iowa. Species composition of regeneration under the canopies of dead elm trees varied among the different types. Celtis occidentalis and Ulmus americana were important species in the regeneration in many of the types. Avian dispersal of seeds was important in the replacement process. Epidemics of tree diseases not native to North America have caused significant changes in forest composition. The importance of disease in determining forest composition and in initiating new patterns of secondary succession has been emphasized by Woods (1953). The bestdocumented example of this phenomenon is the change in forest composition brought about by the chestnut blight in the eastern United States (Korstian and Stickel, 1927; Keever, 1953; Nelson, 1955; Woods and Shanks, 1959). Dutch elm disease, a wilt disease caused by Ceratocystis ulmi, is eliminating American species of elm from many forests and cities of the eastern and midwestern portions of the United States and adjacent areas of Canada. The degree to which elm species will be eliminated remains to be seen; large numbers of trees, however, have already been killed. The disease was first reported in the United States in Ohio in 1930. Since that time it has spread into 30 other states, the District of Columbia and three Canadian provinces (Wysong and Willis, 1968). Dutch elm disease was first reported in Iowa in 1957 (Iowa Coop. Ext. Serv., 1957). From initial loci in central and southeastern Iowa (Holmes, 1962), the disease had spread to 94 of the 99 counties in the state by 1967 (Wysong and Willis, 1968). Mortality was especially evident in the forests of southeastern Iowa. These forests have a high recreational potential and contain a number of state parks. Elms have contributed substantially to the attractiveness of these parks. Their loss is noticeable at the present time. Their replacement through secondary plant succession or by planting will affect the future quality of these parks. This study was undertaken to investigate the changes in species composition that were occurring in the forests of southeastern Iowa and to determine those factors important in the process of natural replacement of disease-killed Ulmus americana.

GEIS, J. W. and W. R. BOGGESS (Univ. Illinois, Urbana). Soil-vegetation relationships in a prairie grove remnant. Bull. Torrey Bot. Club 97: 196-203. 1970.-The distribution of soils and woody vegetation is closely correlated in a 24-heetare prairie-grove remnant in Champaign County, Illinois. Although the site has been forested for an estimated 400 to 600 years, soil development has been retarded by excessive moisture conditions, and the soils on 71% of the area are morphologically identical to the Brunizem and Humic Gley soils developed under the original tall grass prairie. An overstory of dead elm (predominantly Ulmus americana), Celtis occidentalis, and Quercus macrocarpa, along with a heavy shrub cover of Lindera benzoin, Euonymus atropurpureus and Xanthoxylum americanum occurs in low physiographic locations on Humic Gley soils. Acer saccharum, Q. rubra, C. occidentalis, U. rubra, and Aesculus glabra dominate a mixed hardwood complex in relatively flat physiographic areas in which Brunizem soils persist. Soils transitional between Brunizem and Gray-Brown Podzolic soils have developed in areas of greatest topographic relief. Acer saccharum dominates these transitional sites, along with Q. rubra, Tilia americana, and C. occidentalis. Species distribution and soil pattern are similarly related to a physiographically based gradient from hydromesic conditions in low-lying and depressional areas to mesic conditions in areas of greatest topographic relief.

Quantitative data for trees, saplings, tree seedlings, shrubs, herbs, and environmental characteristics were collected in seven forest stands in the Harvey N. Ott Preserve., Calhoun Co., Michigan. Two lowland stands were sampled utilizing standing dead elms and live trees only to assess the impact of Dutch elm disease. Surveyors' records were examined to reconstruct the presettlement vegetation. A two- dimensional ordination, based on the densities and basal area per acre of 13 tree species, was used to illustrate canopy structure, and frequency values for 12 shrub species and 29 herb species were used to demonstrate subcanopy structure. The presettlement upland vegetation was oak savanna whereas the present upland vegetation is second-growth oak forests. The effect of past and recent fires, soil water retaining capacity, and pH on forest development is discussed. Larix laricina had a broader range in the lowland vegetation during presettlement times than at present. Ulmus americana is now rapidly disappearing due to Dutch elm disease. Changes in the lowland vegetation are correlated with changes in drain- age patterns, depth to water table, and disease.

early as usual on account of the severe drouth during the summer and autumn. Only leaves of Juglans nigra (walnut), Asimina triloba (papaw), Ulmus americana (American elm), Malus sylvestris (apple), and Catalpa spp. (catalpa) remained on the trees after the freeze and not until November 18 did they all come down. This is particularly unusual. When they did come down it was almost as a rain of leaves. This is the first time I have ever known catalpa leaves to fail to come down promptly after a freeze. A tree of Acer ginnala still had 5 per cent of its dead leaves hanging on the following spring.

Osborne county is situated in the north central part of Kansas, about 30 miles from the Nebraska line and about 170 miles east of the Colorado line. It has about 900 square miles, being thirty miles on each side. The first census, taken in June, 1871, showed 724 inhabitants, 281 of which were eligible to vote. The county was organized in the fall of 1871 and named after Vincent B. Osborne, a private of company A, Second Kansas cavalry. The chief cultivated crops of Osborne county are wheat, corn, sorghums, and alfalfa. Beef and dairy cattle, hogs and poultry are the chief live stock. Considerable grazing is carried on over the hilly portions of the county. The annual average rainfall is about 20 inches, 80 per cent of which falls in the growing season. Both the north and south branches of the Solomon river pass through the county. The former cuts through the northeast corner from Portis to Downs, while the latter passes through the entire county from west to east, passing near Alton and Osborne and thence eastward, uniting with the north fork a few miles east of the Osborne county line. A number of smaller streams flow northeastward into the South Solomon. These are Medicine creek, Kill creek (two branches), Covert creek, Indian creek, and other minor streams. The extreme southern portion of the county drains southward. All these streams have a fringe of trees. These are largely Ulmus americana, Ulmus fulva, Populus sargentii, Salix amygdaloides and Quercus macrocarpa interspersed with Celtis occidentalis, Salix nigra, and in some places Juglans nigra. In many of the swampy spots Salix longifolia is common. It is to be regretted that the few native trees in the county are being so rapidly cut down for fuel. However, it is gratifying to note that a number of low waste places are being planted to the elms and poplars. The county as a whole is rolling to quite hilly. The highest elevation in the county is east of Covert and is about 2,000 feet above sea level. For the most part the hills are composed of limestone gravel, but in many places they are quite rocky. The characteristic flora of these hills are such plants as Viorna fremontij, Polygala alba, Leucelene ericoides, Townsendia exscapa, Senecio plattensis, Tetraneuris fastigata, and Arenaria texana. In most of the upland valleys the common trees are Celtis occidentalis, Ulmus americana, Ulmus fulva and Quercus macrocarpa. A few of the common shrubs in these valleys are Rhus toxicodendron, Rhus trilobata and Ceanothus ovatus pubescens. A number of species of plants seem to be quite rare in the county. For instance, in my survey of the county for plants only one specimen of Sonchus asper was found. Celastrus scandens was found in but a few places and is confined to the wooded creeks or river banks. The small legume, Acmispon americanus, was found only in a certain pasture about three miles south of Downs. I found but two specimens of Plantago lanceolata, and these were near a small-town lawn. Two small mud-loving plants, Cyperus inflexus and Heteranthera limosa, were found only at the edge of a pond six miles northeast of

Sprouts and tops of American elm (Ulmus americana) were preferred woody deer browse on the Allegheny National Forest in northwestern Pennsylvania. More than 90 percent of the succulent sprouts and two-thirds of the available twigs in the tops of trees felled in winter were utilized in the growing season after cutting. Elm was found to sprout vigorously from stumps, and from the boles of trees that were successfully hinged to the stumps. These results are in general contrast to reports in the literature on deer browse in which elm is listed as low in use. The white-tailed deer (Odocoileus virgianus) has the reputation of being a highly selective feeder, browsing heavily on some plants, nibbling lightly or not at all on others. This paper reports on heavy utilization of American elm twigs as browse in northwestern Pennsylvania during spring and summer. Observations of the use of elm by deer were made in the late summer of 1964 in a northern hardwood poletimber stand, 40 to 60 years old, on the Allegheny National Forest in northwestern Pennsylvania. About 12 acres had been thinned the previous winter in one of the blocks used to study a method for increasing deer-browse production in poletimber stands (Jordan et al. 1965). Before cutting, elm was common in the stand, comprising up to 10 percent of the stems. Associated species were sugar maple (Acer saccharum), black cherry (Prunus serotina), basswood (Tilia americana), white ash (Fraxinus americana), yellow birch (Betula alleghaniensis), hop-hornbeam (Ostrya virginiana), and blue beech ( Carpinus caroliniana). Slippery elm (Ulmus rubra), beech (Fagus grandifolia), quaking aspen (Populus tremuloides), black birch (Betula lenta), eastern hemlock (Tsuga canadensis), red maple (Acer rubrum), and striped maple (A. pensylvanicum) were less common, occurring mainly as isolated trees. Under the stand-improvement method used, all stems except selected future crop trees were cut to produce browse. Wellformed sugar maple, white ash, and black cherry were favored in the residual stand. In the late summer following cutting, a randomized sample of woody browse production and utilization yielded the following number of twigs per acre and percent of browsing by species: sugar maple 183,900, 6.4; yellow birch 52,900, 15.7; hophornbeam 28,800, 6.6; basswood 14,400, 59.0; white ash 11,000, 23.6; black cherry 8,700, 21.8; blue beech 6,800, 0.0; beech 1,700, 11.8; and striped maple 300, 0.0. In felling, an effort was made to hinge the stem to the stump so that the top would remain alive to produce browse in succeeding years. Thus browse was produced by both the stumps and tops, and in many instances along the bole of the tree. American elm was found to sprout vigorously from the stumps, and from the boles of trees that were successfully hinged. To determine the extent to which American elm was browsed, individual trees accessible to deer were selected, and all browsed and unbrowsed twigs 2 inches or more in length to 5 ft in height were recorded. The twigs were grouped into three categories: stump sprouts, stem sprouts, and tops.

The 1952 season was not particularly favorable for the development of fructifications of fungi as compared with the season of 1951 which had almost ideal moisture conditions. A deficiency of rainfall occurred throughout most of the season with drought conditions existing from the latter half of August through the remainder of the year. The saprophytic flora was curtailed and the collections of fleshy fungi were few. Several of the plant pathogenic fungi which in 1951 threatened to build up to epiphytotic proportions were completely checked by the dry conditions of 1952. For example, Dothistroma pini Hulbary, which is believed to be the cause of the serious needle-blight disease of pines, was not observed on any of the new needles produced in 1952 although abundant fruitbodies and spores were present on the 1950-51 meedles. Apparently the dry conditions, especially during May and June (3 inches of rainfall in 1952 compared with 17 inches for the two months in 1951), prevented infection of the developing needles. Fruitbodies of Dothistroma pini were found on two additional species of pine which were formerly thought to be resistant. On white pine (Pinus strobus L.) needle-blight symptoms were similar to those on the other susceptible pines (Austrian, western yellow, lodgepole and Swiss mountain pines), but on table mountain pine (Pinus pungens Lamb.) yellowish spots on only a few needles were noted. This is the first report in the United States of Dothistroma pini on these two species. Perhaps the most interesting fungus record new for Kansas was Ascoidea rubescens Brefeld & Lindau, a primitive ascomycete found in the slime flux of American elm (Ulmus americana L.). A brownish feltlike mat of mycelium was developed on the moist slime flux in which broad hyphae bore terminal cells (the asci) containing many hat-shaped ascospores similar to those produced in some yeast fungi. Single-celled, hyaline conidia were also produced on stout, erect conidiophores. The fungus was first collected in October on an old elm tree along Wildcat Creek. Later the fungus was found by S. M. Pady to be fairly common on elm trees on the Kansas State College campus and along the streets of Manhattan. Dr. Pady was able to culture the organism but only the

A complete census was made in a bottomland forest near Norman, Oklahoma, in 1956. Of the 13 tree species encountered, green ash (Fraxinus pennsylvanica var. subintegerrima) was the only dominant. American elm (Ulmus americana), cottonwood (Populus Sargentii) and persimmon (Diospyros virginiana) were important secondary species. The considerable number of dead trees, the paucity of saplings, and the data from previous studies suggested that this forest had be deteriorating since 1948. A complete census of the tree population in a green ash bottomland forest was accomplished in the autumn of 1956. The stand analysed, known as the Oliver Wildlife Preserve, is located on the highest level of the South Canadian River, about two miles south of Norman, Oklahoma. In 1948 the area was very wet as indicated by the presence of the aquatic water-willow weed and liverwort-moss collars on the bases of most of the trees (Penfound 1948). Since 1948 the precipitation has been much below normal, especially in the even-numbered years of 1952, 1954 and 1956. As a result the liverwort-moss collars have disappeared, many seedlings of the eastern red cedar have appeared, and a considerable number of trees have died, especially since 1952.

Plantae brevissimae (5 mm.), superne viridiores, inferne nigrae. Caulis cylindricus; vena media inchoata vel nulla. Folia glabra, spatulata, apice subacuto. Costa supra medium evanescens. Cellulae basilares rectangulares; cellulae medii et superioris folii similes, subquadratae, chlorophyllosae. Flores et fructus ignoti. Propagatio innovationibus basilaribus et propagulis abundantibus, inferne partis in facie dorsali foliorum. Propagula fere cylindrica. Plants growing in dense clusters in soot-filled crevices of bark. Plants easily separated from the substrate and from each other; short, rarely over 5 mm. in height, dark green above, blackish below. Stem circular in cross-section, central strand rudimentary or none. Leaves 1.2 X 0.3 mm., spatulate with subacute tip. Costa % the length of the leaf, 55 ,/ in width in the lower portion, smooth, in cross-section with 2 (rarely 3) ventral guide cells, dorsally of 9-13 stereids. Basal cells rectangular, up to 50 X 25 ,u, smooth with the exception of the propagula-bearing "papillae"; median and upper leaf cells similar, roundish-quadrate to 5and 6-sided, a few rectangular, smooth, with slightly thickened walls and indistinct trigones, averaging about 25 ju in diameter. Sex organs and sporophyte unknown. Reproduction by basal innovations and numerous propagula borne on the dorsal surfaces of the basilar regions of the leaves. Propagula-bearing cells differentiated only by the papilla-like spurs on which are borne the propagula. Propagula generally cylindrical, a few of bizarre form, smooth, densely chlorophyllose, divided at right angles to their longitudinal axes, and often muriform divided. Primary divisions none to six, depending on the size of the propagula. Width of the propagula usually about 40 ,, length up to 200 /. TYPE: On the bark of an American Elm (Ulmus americana L.) on the F. F. Van Deventer estate, 862 Temple Ave., Knoxville, Tennessee, alt. 950 ft. Dec. 27, 1932. The type material is deposited in the Herbarium of The University of Tennessee. The short costa and lack of papillae suggest perhaps another or new genus, but if the sporophyte is considered more conservative than the gametophyte, it seems this species should be left in Tortula until the sporophyte is discovered. The areolation of the leaves is similar to that of many species of Tortula and the gross appearance is almost identical with that of Tortula caroliniana Andrews. The propagula are similar in structure to those of T. caroliniana Andrews with the exception that the latter are papillose. Those of Andrews' species are also borne in the upper part of the leaf, Andrews' states "from the ventral surface," but in Pringle's Plantae Mexicanae, No. IO618, in the Yale Herbarium, they are

The first complete inventory of the woody vegetation of Brownfield Woods since 1925 was completed in 1960. This 60-acre woodland is a remnant of a large prairie grove that once occupied an area of 10 square miles northeast of Urbana, Champaign County, Illinois. The stand is mixed mesophytic in composition with 113 trees per acre (3 inches and above in diameter) and a basal area of 114 sq. ft. Twenty-five woody species were tallied with sugar maple (Acer sac- charum Marsh) the leading dominant. The most striking change in the vegetation since 1925 was the 60% increase in the basal area of sugar maple, and a corresponding decrease in that of elm (Ulmus americana L. and U. rubra Muhl.). The latter is due to mortality from phloem necro- sis and the Dutch elm disease. A heavy understory, dominated by sugar maple, has developed. Nearly two-thirds of the trees less than one inch in diameter are sugar maple thus suggesting a continued, or increasing dominance of this species. There have been striking changes in the woody vegetation of Brownfield Woods during the past 35 years. Many of the large trees mentioned by Telford (1926) are still alive, but mortality has been heavy, particularly among the elms. A heavy understory of seedlings and small saplings has developed, aided no doubt by more than 20 years of complete protection from fire, grazing, and public use. Some of these changes, and their implications, are discussed in this paper.

Observations were made in Ottawa County, Michigan, during 1960-61, on percentages of native elms showing symptoms of Dutch elm disease. The percentage of elms affected depended partly on dispersal, the disease spreading northwestward through the county. In 1960, a density-dependent relationship existed between the disease and its host, areas of low elm density having lower percentages of affected trees than areas of high density. In 1961, even areas of low elm density tended to have high percentages of dead and dying trees. INTRODUCTION The spread of Dutch elm disease (caused by the fungus Ceratocystis ulmi (Buisman) C. Moreau) in eastern North America appears to offer an ideal situation for examination of some aspects of the ecology of populations. Nevertheless, studies of such a nature have been few; nearly all of the vast literature deals with gross aspects of the spread of the disease and with evaluation of methods of possible control. This study examines the geographic pattern of infection, as related to dispersal and elm density, in the southern three-fourths of Ottawa County, Michigan, between June, 1960, and July, 1961. Thanks are directed to J. C. Carter and S. C. Kendeigh for critical examination of the manuscript. PROCEDURE All highways and major secondary roads were traversed. The total number of native elms, Ulmus americana and U. rubra, and the total number of elms showing the wilting and defoliation characteristic of the disease were counted in one-mile samples on one side of each road to a depth of one city lot (about 165 feet). The sample for July, 1960, included 224 linear miles and 3868 trees; the sample for May-July, 1961, 161 miles and 2735 trees. No attempt was made to eliminate diseases other than Dutch elm disease, but it is thought that these did not influence the results appreciably. RESULTS Dispersal.-The most noticeable feature of the data of 1960 is a trend of increasing frequency of infection toward the southeastern corner of the county (Fig. 1). This pattern probably was the result of dispersal following an initial invasion from the southeast. The disease was reported from Kent County, lying directly to the east, in 1955, one year before it was reported from Ottawa County (Michigan Dept. Agric., 1960).