Title: Botanical characters of the leaves of the date palm used in distinguishing cultivated varieties
Identifier: botanicalcharact223maso (find matches)
Year: 1915 (1910s)
Authors: Mason, Silas C. (Silas Cheever), b. 1857
Subjects: Date palm; Leaves; Date palm
Publisher: Washington, D. C. : U. S. Dept. of Agriculture
Contributing Library: U.S. Department of Agriculture, National Agricultural Library
Digitizing Sponsor: U.S. Department of Agriculture, National Agricultural Library

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CHARACTERS OF THE LEAVES OF THE DATE PALM. The broad outlines of the blade vary considerably with varieties and are determined by the length of the pinna? in different parts of the blade and the angles which they form with the rachis and plane. To illustrate: If in a given leaf the pinnae at the middle of the blade are 16 inches long and placed at right angles, or 90°, with the rachis and lie in the plane of the blade; that is, so that the leaf is flat, the leaf will be 32 inches broad, not count- ing the breadth of the rachis fig. 2, A, lb). Let the same length of pinnae be placed in- clined only 45° from the rachis and still in the plane of the blade, then the blade will be but 22f inches broad (fig. 2, A, cc). But let the pinna?, instead of lying flat (fig. 2,B, b) diverge 45° from the plane of the blade, as well as 45° from the rachis (fig. 2, B, c), then the leaf blade be- comes a V-shaped trough only 16 inches broad, or half the breadth of the blade with the pinnae flat and at right an- gles. THE RACHIS. A close inspection of the rachis of the date leaf shows that it is irregularly four- sided; the inner or ventral surface is usually strongly arched or at the first spines is made up of two ogee curves turned together. The back or dorsal surface is moder- ately or often strongly different
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Fig. 1.—A typical date leaf, showing its various parts. rounded at the base, slightly rounded or rarely flattened toward the

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