LECT. VII.] ANATOMY OF STEMS. 303 



monocotyledons, I shall follow the description of 

 Mirbel, in explaining to you the growth of a Palm. 

 When the young plant, rising from the seed, ap- 

 pears at the surface of the ground, the leaves, 

 originally folded up and sheathed within each 

 other, separate themselves, increase in number, 

 and form a sheaf-like group. Those on the cir- 

 cumference now spread out, perform their func- 

 tions, and are detached ; but their bases re- 

 maining, form a solid or ligneous ring, which 

 is the origin of the stem. Within this circle the 

 sheaf of leaves rises vertically ; owing, perhaps, 

 to the resistance at the circumference ; and the 

 exterior ones having spread out on every side in 

 the same manner as the former, drop after a time, 

 also, and leave their bases to form another circle ; 

 within which the sheaf still rising, again spreads 

 out another range of leaves ; and in this way the 

 stem is gradually formed by the evolution of the 

 terminal leaf-bud, and the induration of the 

 footstalks of the fallen leaves. The whole stem 

 displays the cicatrices of the successive circles of 

 detached leaves, and these becoming hardened 

 by their exposure to the air, and the ligneous 

 bundles within them being older, in a direct ratio 

 as they are nearer to the surface (the development 

 of parts always taking place in the centre), the 

 substance of the stem is necessarily softer within, 

 and harder as it approaches the circumference. 



