. Plant studies; an elementary botany. Botany. 42 PLANT STUDIES but it usually occurs, and does not necessarily imply ex- treme conditions of any kind. However, palisade tissue of unusually narrow and elongated cells, or forming two or. Fig. 32. Section through a portion of the leaf of the yew (Taxus), showing cuticle (c), epidermis (e), and the upper portion of the palisade cells (p). three layers, indicates exposure to intense light or drouth, and is very characteristic of alpine and desert plants. The accompanying illustration (Fig. 31) shows in a striking way the effect of light intensity
. Plant studies; an elementary botany. Botany. 42 PLANT STUDIES but it usually occurs, and does not necessarily imply ex- treme conditions of any kind. However, palisade tissue of unusually narrow and elongated cells, or forming two or. Fig. 32. Section through a portion of the leaf of the yew (Taxus), showing cuticle (c), epidermis (e), and the upper portion of the palisade cells (p). three layers, indicates exposure to intense light or drouth, and is very characteristic of alpine and desert plants. The accompanying illustration (Fig. 31) shows in a striking way the effect of light intensity upon the structure of the mesophyll, by contrasting leaves of the same plant exposed to the extreme conditions of light and shade. The most usual structural adaptations, however, are connected with the epidermis. The outer walls of the epi- dermal cells may become thickened, sometimes excessively so ; the other epidermal walls may also become more or less thickened; or even what seems to be more than one epi- dermal layer is found protecting the meso- phyll. If the outer Fig. 33. Section through a portion of the leaf of walls of the epidermal carnation, showing the heavy cuticle {at) -i i , ⢠, formed by the outer walls of the epidermal C e 11 S COlltlllUe t O cells (ep). Through the cuticle a passageway thicken, the Outer re- leads to the stoma, whose two guard-cells are â -f fl tl ' 1 11 seen lying between the two epidermal cells »10n 0I t110 U11CK WaU shown in the figure. Below the epidermal loses its S 11' U C t U 1' e cells some of the palisade cells (,M0 are shown ;md formg th cuUde containing cnkiroplaets, and below the stoma t ' ie seen the air chamber into which it opens. W ll i C ll is OUe of the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Coulter, John Merle, 1851-1928. New York, D. Ap
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