168 



PHYSIOLOGICAL BOTANY. 



absorption is largely helped by root hairs, which clothe 

 the root and rootlets, as seen in Figs. 519, 520. Fig. 

 519, root of a Maple sprinkled with hair-like processes 

 or minute fibrillse ; these are usually each a single 

 elongated cell, and appear on the newer parts of the 

 root, a little distance from the growing point, dying or 

 becoming useless on the older parts. The Boot, as to 

 use, form, etc., is treated in another place (see Chapter 

 XIII., Structural Botany). 



CHAPTER IV. 



MONOCOTYLEDONOUS STRUCTURE. 



421. The woody fibers and vessels that make up 

 the stems of Palms, Indian Corn, Bamboo, Sugar Cane, 

 and all grass-like plants, are not arranged as they are 

 in the Oak, Maple, and Apple, already described. A 

 cross-section of a Palm stem presents 

 a mass of pith, dotted all over with 

 sections of woody fiber and vessels 

 without any apparent order of ar- 

 rangement (521); the whole inclosed 

 in a circular ring or rind, in which 

 the fibre-vascular bundles are smaller 

 than in the body of the stem. In a 

 longitudinal section the threads of woody fiber may 

 be traced from the bases of the leaves in a curve out 

 toward the center, and in a recurve back again to the 

 side whence they started (Figs. 522, 523). In stems 

 like the Indian Corn and the Grasses, with long spaces 

 between the leaves and closed nodes, the fibro-vascular 

 threads extend in straight lines from node to node, 



521, Cross-section of the trunk 

 of a Palm. 





