File:The American botanist and florist; including lessons in the structure, life, and growth of plants; together with a simple analytical flora, descriptive of the native and cultivated plants growing in (14596008337).jpg

Identifier: americanbotani00wood (find matches)
Title: The American botanist and florist; including lessons in the structure, life, and growth of plants; together with a simple analytical flora, descriptive of the native and cultivated plants growing in the Atlantic division of the American union
Year: 1870 (1870s)
Authors: Wood, Alphonso, 1810-1881
Subjects: Botany
Publisher: New York, Chicago, A.S. Barnes & company
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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lude thetissues beneath it from the external air, but is cleft here andthere by little chinks called stomata (mouths). Each stoma isguarded by a pair of reniform cells, of such mechanism (not wellunderstood) as to open in a moist atmosphere and close in a dry. 398. The stomata are always placed over and communicate with the intercellular pas-sages. They are found only on the green surfaces of parts exposed to the air, mostabundant on the under surface of the leaves. Their numbers are immense. On the leafof garden Rhubarb 5,000 were counted in the space of a square inch ; in the garden Iris,12,000 ; in the Pink, 36,000 ; in Hydrangea, 160,000. 399. The surface of the epidennis at length becomes itself coated with a delicate, trans-parent pellicle, not cellular, called the cuticle. It varies in consistency, being thickerand stronger in evergreen and succulent plants. It seems to be merely the outer cell-wall of the epidermis thickened and separated from the newly-formed wall beneath it.
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497 498 497, Cells and stomata of the epidermis of Oxalis violacea; and 498, of ConvHllaria racemosa. 400. The hairs which clothe the epidermis are mere expansions of its tissue. They may each consist of a single elongated cell, or of a row of cells. They may also be simple, or branched,or stellate, or otherwise diversified. 401. Glands are cellular structures serving to elaborate andcontain the peculiar secretions of the plant, such as aromaticoils, resins, honey, poisons, etc. A gland may be merely an ex-panded cell at the summit of a hair, or at its base, and hence 132 PHYSTOLOGICAL BOTANY. called a glandular hair (Labiatse). Or it may be a peculiar cellunder the epidermis, giving to the organ a punctate appearance(leaf of Lemon). Other glands are compound, and either external(Sundew) or internal reservoirs of secretion (rind of Orange), 402. Stings are stiff-pointed, 1-celled hairs expanded at baseinto a gland containing poisonous secretion. An elastic ring ofepidermal cells press

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