INTERNAL STRUCTURE. 



71 



buds are freely developed (as in the Asparagus) , or the leaves 

 are scattered along the stem or branches by the full development 

 of internodes (as in 



m 



the Bamboo, Maize, 

 &c. ) , the}' gradually 

 taper upward in the 

 manner of most ex- 

 ogenous stems. 



137. This kind 

 of stem comprises 

 several subordinate 

 types as to internal 

 structure, which to 

 be well understood 

 must be studied his- 

 tologically, under the 

 microscope. 1 To one 

 of these, by no means 

 the simplest, belongs 

 the ordinary palm- 

 stem, the anatomy 

 of which was made 

 classical by Mohl, 

 and has been 

 supplemented 

 by Naegx-li. 

 In this a large 

 part of the 

 bundles, or all 

 of the more 



conspicuous kind, starting from the base of the leaf to which 

 they respectively belong, curve inward more or less strongly 

 toward the centre of the stem, and thence gradually outward 

 as they descend until they reach the rind, in which the 

 attenuated lower extremity mostly terminates. Consequently, the 

 bundles from different heights cross in their course, somewhat 



1 For the best and most accessible memoir on the subject, of recent date, 

 see Guillaud, Recherches sur 1'Anatomie comparee et le De'veloppement des 

 Tissus de la Tige dans les Monocotyledones, published in Ann. Sci. Nat. 

 ser. 6, v. 1-176, 1877. Six types of the stem of Monocotyledons are here 

 recognized by anatomical characters and modes of growth, one of them 

 having four modifications. 



FIG. 126. Sabal Palmetto in various stages ; also the Yucca aloifolia or Spanish 

 Bayonet. 



