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An enzymatic digestion procedure is presented which allows for the isolation of large quantities of mesophyll cells and minor veins of Nicotiana tabacumL. cv. ‘Wisconsin 38’. Isolated mesophyll cells exhibited CO2fixation rates in excess of 150 μmoles CO2mg chl‐1hr‐1, while bundles consistently fixed CO2at much lower rates, viz. 10–20 μmoles CO2mg chl‐1hr‐1. Various physical and biochemical parameters of the isolates have been compared with intact leaf disks.

The effect of 2 MHz ultrasound at intensity levels from 1 to 20 W/cm2on growth rate, lateral root formation, mitotic index and chromosome morphology was studied. The ultrasound produced an immediate reduction in growth rate on the first post-exposure day followed by recovery to control value after ten days. Ultrasound reduced lateral root formation and mitotic index. Intensity and time dependent relations were found for growth rate reduction and lateral root formation. No “classical” chromosome aberrations were found but chromosomal anomalies—bridged prophases and metaphases and agglomerated metaphases—of another nature were observed after sonication: these anomalies were quantitated into a damage index.

CLINICALLY evident cysts of the alveolar and palatal mucosa are apparently a very common finding in newborns and infants and are often referred to as Epstein's pearls or Bohn's nodules. The cystic lesions have been described as white, raised, multiple nodules of maxillary and mandibular alveolar ridges and midpalatal region varying in size from a pin head to 2 or 3 mm. The majority of these cysts are inconspicuous and usually only the larger lesions are noticed. No treatment of these lesions is required as they do not interfere with tooth eruption and usually disappear in a few months.Palatal mucosal cysts of fetuses and infants have been studied in detail by several investigators.1-3 Monteleone and McLellan1 found 79% to 85% of 393 1-day-old infants had cystic nodules in the median palatine raphe at the junction of hard and soft palates and histologic examination revealed cysts containing keratin. Burke

Mucoceles involving the oral mucous glands are common lesions occurring in approximately 5.6% of oral biopsies. Of the 594 cases comprising this study 88% were diagnosed at the initial clinical examination. Characteristically they consist of a soft fluctuant bluish or translucent swelling varying in size from a few millimeters to several centimeters. They are most commonly found on the lower lip, but may also occur on the buccal mucosa, floor of mouth, palate, upper lip, and tongue. Mucoceles are found in all age groups but are most frequent in children and young adults. Traumatic injury to a duct or ducts with injury or severance of the duct is the usual etiologic factor. Mucus subsequently escapes into the adjacent tissue and forms a cyst-like space surrounded by granulation tissue rather than epithelium. Cystic spaces lined with epithelium are seen in very few instances.

NONCALCIFIED benign neoplasms are commonly seen on the tongue and are usually located on the lateral borders in the anterior two thirds. The ventral surface and posterior third of the tongue are rare sites for benign neoplasms. Benign tumors of the tongue containing cartilage and so-called mixed tumors containing cartilage, fibrous connective tissue, and bone have also been reported.1-7 True osteomas of the tongue, however, are exceedingly rare lesions and, in reviewing the literature, only eleven cases have been reported.8-18 A 12th case is to be presented (the table). In all but one case, the patients were females. The oldest patient was 39 and the youngest 11. With the exception of the 11 year old, the remainder of the patients were in their 20's and 30's. The average age of the patients was 25 1/2 years. The most common presenting complaint was difficulty in swallowing although

The ultrastructure of minor veins of Beta vulgariswas examined with reference to possible models for vein loading of translocate. Structural evidence was reviewed in the light of recent physiological observations as a basis for proposed mechanisms. Features which appeared to be of significance in formulating a model included the open, differentiated sieve plates, the predominance of organelle‐rich parenchyma cells, and the branched plasmodesmata connecting sieve tubes and parenchyma cells. The resulting model views cell to cell movement of photosynthate via the symplast to the specialized parenchyma cells. The actively accumulated sucrose appears to move from the specialized parenchyma cells into the sieve tubes via plasmodesmata in the lateral and end walls.

Oral lesions of pemphigus are a common manifestation of the disease, and often precede the severe skin involvement. The histopathology of the oral lesion is invariably diagnostic for pemphigus. The oral cytologic smear is highly suggestive of the disease. Where a diagnosis with grave implications is to be made, as for pemphigus, all available diagnostic criteria should be utilized. These should include both the oral biopsy and the oral cytologic smear.

We give a motivated introduction to the theory of perverse sheaves, culminating in the decomposition theorem of Beilinson, Bernstein, Deligne and Gabber. A goal of this survey is to show how the theory develops naturally from classical constructions used in the study of topological properties of algebraic varieties. While most proofs are omitted, we discuss several approaches to the decomposition theorem and indicate some important applications and examples.

A method is proposed for analysis of total nitrogen in plant tissues enabling predigestion (to reduce nitrate to ammonium) and digestion to be performed in a Folin‐Wu tube. Following digestion, a sensitive colorimetric assay for ammonium is used to quantitate N‐content in an aliquot of the digest. The proposed method has several advantages: 1) up to 110 tissue samples can be predigested and digested in one batch; 2) small tissue samples (5 to 100 mg) can be accommodated; 3) the colorimetric assay for ammonia is very sensitive; 4) tissues can be predigested to recover all nitrate in the samples; and 5) aliquot size from the diluted digest can be varied to effectively detect as little as 1 µg of N.

This paper is partially based on work performed under contract with the U. S. Atomic Energy Commission at The University of Rochester Atomic Energy Project and has bcen assigned Report No. UR-3490-238, and has also been partially supported by Grant USPHS GM0933.

Editorial Note:This article was prepared for the IV Pan American Congress of Social Service held in San Jose, Costa Rica in November, 1961. It is followed by the text of a resolution on the Alliance for Progress adopted by the Congress.

IN RECENT years there have been far too many casual and unsupported statements concerning the reliability of biopsies and cytologic smears in the diagnosis of oral cancer and other oral lesions. There are, to date, surprisingly few carefully controlled studies in which significant numbers of oral lesions have been subjected to both cytodiagnostic and histopathologic evaluation and study in each instance.1,2 Many studies in oral cytology have presented data that are not well substantiated, since biopsies were not obtained in all cases.3,4 The problems of this type of study have been discussed.5,6False positive results in cytologic evaluation present no significant problem, since immediate follow-up and biopsy is mandatory in order to confirm the diagnosis of carcinoma. False negative results in cytologic evaluation present a real hazard in cancer management, since biopsy will often not be done until such time as the clinical features of a proliferating