Epidermal Hair Research Articles

Fruit Morphology and Anatomy of the Cherimoya

1. Fruits of Annona cherimola Mill. can be segregated into horticultural groups based on the nature of the fruit form and surface characters. 2. Considerable variation in density of epidermal hair and stomata is found between fruits of different horticultural varieties and between different parts of the fruit. 3. The bulk of the carpellary wall is parenchyma, the outer portion of which contains sclereid masses. These masses of sclerenchyma have modified parenchymatous cells radiating outward from them. 4. The vascular supply for each carpel is derived from a central reticulate vascular cylinder in the receptacle. Each carpellary bundle divides into three strands upon entering the carpel. One strand supplies the ovule; the other two become the dorsal and ventral bundles. 5. Starch is the prominent ergastic material found throughout the parenchyma in the firm mature fruit but disappears rapidly and completely as the fruit softens. Oil idioblasts are scattered through the parenchyma of the carpellary wall and of the endosperm of the seed. 6. The seed coat consists of heavily lignified, sclerenchymatous layers. The inner surface of the inner integument is characterized by a layer, one or two cells in thickness, in which the cells show extreme variability in shape and are separated by conspicuously large intercellular spaces. 7. The cells of the convolute endosperm are filled primarily with starch, although a number of oil idioblasts occur, particularly near the periphery.

CELLULOSE AS A SUBSTRATUM FOR SAPROPHYTIC CHYTRIDS

SINCE APRIL, 1938, collections of saprophytic chytrids have been made from bait placed in ponds near the Thames River on the campus and in a sphagnum bog at North Bay, Ontario. The method of baiting was that used by Karling (1935). A number of these chytrids are being kept in culture. In general, methods and technique followed are those described recently by Couch (1939) and brought here by Miss Berdan from his Chapel Hill laboratory after the summer of 1938. All cultures have been kept under as nearly sterile conditions as possible in a room with controlled temperature (about 60?F.). Until January 30,1939,the substrata used were leaves of wheat, corn, rye, oats, other cereal grains, and grasses from which the chlorophyll had been removed. There are some practical disadvantages in their use. One is the necessity of keeping the plants in young stages all year in the greenhouse. Secondly, the thickness of the leaves, the presence of stomata, the epidermal hairs, and even the cell walls often tend to obscure the early stages of growth from the germinating zoospores. Very young, thin leaves are used to offset this, but their tissues break down rapidly, and the cultures require constant care. Even with older leaves, some chytrid species develop so rapidly that water and substratum have to be changed every few days. When several hundred cultures are being kept over long periods, the labor and inconvenience are excessive. During a conversation in January, 1939, Dr. F. K. Sparrow, Jr., suggested the use of paraffined filter paper as a substratum, following Dr. Rex Webster (Middlebury College, Vermont), who had grown a species of Rhizidiomyces2 upon it. More than fifty years ago, according to Schr6ter (1889), Rhizophlyctis rosea (de Bary and Woronin) Fischer was found on moist blotting paper by Sorauer in Germany. OBSERVATIONs.-It had been noticed in our laboratory that most of our forms seemed to thrive equally well in leaves lacking nearly all cell contents as in those (e.g., young wheat) with globules of brown oil. Consequently, lens paper (Cenco) in which the individual fibers could be distinguished under the microscope was substituted for paraffined filter paper. On January 30 a small rectangle of this was added to a healthy culture of Rhizophlyctis

THE MELANOTIC PIGMENT IN THE SKIN, HAIR AND EYE OF THE GRAY RABBIT

In the higher vertebrates, especially in man, most of the melanotic pigment is to be found in the ectodermal elements of the skin, where it plays a much more important role than the mesodermal pigment. The pigment building cells (melanoblasts) of the epidermis are the ordinary basal cells, sometimes cells lying directly above them, and cells lying at about the basal cell level but showing dendritic processes. Melanoblasts are also found in the hair matrix cells of the bulb, in the epidermal hair sheets, the epidermal parts of the sebaceous glands, the excretory ducts of the sweat and sebaceous glands and in certain mucous membranes. With the paper of Kolliker in 1860 there began a controversy that lasted for many years as to whether the epidermis built its own pigment or whether it obtained this pigment from the cutis. According to Kolliker, Aebi, Halpern, Riehl and Karg (1860 to 1891),

PIGMENT (MELANIN) STUDIES OF THE HUMAN SKIN AFTER APPLICATION OF THORIUM X

Pigment (melanin) is found in the human epidermis in the basal and overlying cells as well as in a more bizarre appearing cell with dendritic processes. Such dendritic cells are also found in the matrix of pigmented hairs, epidermal hair sheets, sometimes in the epidermal parts of sebaceous glands and in pigmented mucous membranes. They are increased in hyperpigmented processes at the time of pigment formation, especially after exposure to light, x-rays, radium and thorium X. They are well seen in acanthotic processes such as condylomas, lichen ruber, molluscum contagiosum, psoriasis and pemphigus vegetans, as well as in the early stages of melanocarcinomas. In hyperpigmented and acanthotic processes they may be found in the layers above the basal cells. While as a rule it is true that dendritic cells are increased in number and therefore better seen in hyperpigmented skins, for reasons not yet clear they are better visualized in

The Structure and Development of the Bark in the Sassafras

Among the more interesting points brought out by this study are the following: the early thickening of the cuticle; the variation in the number of epidermal hairs and stomata; the early formation of cork in regions exposed to the sun; the stone cells in the outer bark, between the strands of primary sclerenchyma, and in the inner bark; the regular layers of thick-walled phelloderm derived from the secondary phellogens.

A Contribution to the Life History of Apocynum androsaemifolium

IT appears that not one of the Apocynaceae, a family of about iooo species, has ever been studied carefully in reference to the minute morphology of the flower. Considering this in connection with the fact that the family stands near the Asclepiadaceae, with their peculiar pollen and stigma, it was believed that it deserved investigation. Buds and flowers of Apocynum androsaernijolium L. were collected in various stages, and the results of their investigation are herewith described. The order of appearance of the floral whorls is centripetal. The calyx shows no peculiarities other than a ruffling of the epidermis on the abaxial surface near the base, suggesting a mechanism for the folding of the sepals. Each petal of the campanulate corolla has on its inner surface near the base a ridge (fig. i, r) running from the midrib diagonally outward and toward its base. It is highest at the midrib, and undoubtedly functions as an aid in compelling cross-pollination. The ridge arises from the more superficial cells of the leaf, and does not affect the course of the veins. Its meristematic crest forms the cells for its enlargement. The stamens are peculiar in form, adjusting themselves neatly in a ring rather closely applied to the stigmatic head (fig. i, s). At the base of each are two long auriculate appendages (figs. I, 2, 3, ap) extending downwards dorsal to the filament. The sporangia are above the insertion of the filament, and do not extend into the appendages. The loculi open on their inner surfaces, somewhat laterally, by longitudinal slits, and immediately beneath them is a beard of epidermal hairs extending transversely across the faces of the anthers, forming a ring around the stigmatic head (figs. I, 2, b). These hairs meet similar ones from a ring around the head, thus preventing pollen from rolling into the base of the flower.