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Page:Popular Science Monthly Volume 81.djvu/324

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318
THE POPULAR SCIENCE MONTHLY

PSM V81 D324 A fine source of guayule from sierra gojada mexico.png

Fig. 7. Probably the best stand of Guayule in Mexico, Sierra Gojada, Dgo.

The guayule shrub, having the low, tree-like habit of many desert perennials, belongs to the family Compositæ of which our daisies and dandelions are familiar examples. The most obvious proof of this relationship is seen at once in the flowers, which, while not very daisy-like at first glance, are seen in somewhat closer examination to follow the same pattern. Instead, however, of the rather numerous white rays surrounding the yellow center of the well-known daisy, in the guayule the short rays are but five in number, and these, as well as the relatively large disc, are of a uniform pale, dullish yellow. The flowers, unusually for the Composite, have a distinct and very pleasing fragrance, and are visited, and incidentally pollinated, by various small insects, even mosquitoes. The leaves, which may or may not be lobed, according to their development, are clothed with a dense, smooth covering of T-shaped hairs, imparting to them the silvery sheen characteristic of the shrub as a whole.

The smaller twigs are similarly clothed, the hairiness giving way at length to a smooth gray bark, which, with advancing age, becomes longitudinally fissured. On the oldest and largest stems, transverse Assuring takes place. On the whole, however, the surfaces of the branches are smooth and gray, contributing to the general neutral aspect of the plant. But most striking of all the characters is the "feel" of the lesser branches when bent, suggesting a weak wooden rod encased in a firm rubber tube. The branches have little strength, the mechanical elements of the wood being relatively few. An examination of a