. Botany for high schools and colleges. Botany. generally loosely an-anged, with large intercellular spaces be- tween tlicin (Figs. 131 and 133), and these are in free com- munication with tlie external air by means of the stomata. It most frequently happens that this loose tissue is in the under part of the leaf, while the upper portion is composed of one or more layers of closely placed cells ; and tliis agrees with the general distribution of the stomata, there l)oing usually many more on the under than the u|iper surface. 203.—The upper denser tissue, termed 'palisade tissue, is composed o
. Botany for high schools and colleges. Botany. generally loosely an-anged, with large intercellular spaces be- tween tlicin (Figs. 131 and 133), and these are in free com- munication with tlie external air by means of the stomata. It most frequently happens that this loose tissue is in the under part of the leaf, while the upper portion is composed of one or more layers of closely placed cells ; and tliis agrees with the general distribution of the stomata, there l)oing usually many more on the under than the u|iper surface. 203.—The upper denser tissue, termed 'palisade tissue, is composed of elongated cells, which stand at right angles to the surface of the leaf (Fig. 131). In cross-section the palisade-cells are cylindrical, with small intercellular spaces between them (Fig. 132), or in some cases they are more or less compressed and angular. In general, palisade tissue is confined to the upper surface of the leaf, the lower being occu- jned by the loose tissue previously mentioned ; but there are some cu- rious exceptions to this rule. The most notable of these is found in the leaf of Silphium laciniafum— the so-called Compass Plant *—of the Mississippi Yalley; its chloro- phyll-bearing parenchyma is almost entirely arranged as palisade tissue, so that the upper and lowei' por- tions are almost exactly identical in structure (Fig. 134). The ver- tical leaves of the Manzanita of the Pacific Coast {A7^ctostaphylos pungenSj var. platypTiylla) have a similar structure. Section of tne " pali- eade " tissue of the leaf of Echi- vocystis lobata, taken parallel to the leaf surface. A few of the cells drawn with their contained chlorophyll granules. X 250.— From a drawing by J. C. Fig. laS.—Section of the loose parenchyma of the leaf of Echino- cystis lobata, taken parallel to the leaf t-urface. Several of the cells are drawn showing their chloro- phyll granules. X 250.—From a drawing by J. C. Arthur. * For iescriptions of this curious pla
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Keywords: ., bookcentury1900, bookdecade1900, bookpublisher, booksubjectbotany
