196 



BOTANY. 



dying at the end of each year: these are called the annual 

 stemmed species. In other species the aerial stems also 

 persist; the latter are hence known as perennial-stemmed. 



411. The epidermal cells 

 are mostly narrow and elon- 

 gated. The hreathing-pores, 

 which are present in all the 

 chlorophyll-bearing parts of 

 the plant, are arranged with 

 more or less regularity in 

 longitudinal rows ; on the 

 stem they occur in the chan- 

 nels between the numerous 

 ridges. 



Fig. 108. 



Fia. 109. 



FiQ. 108.— Part of a green stem of the Great Horsetail (Equisetum telmateia), 

 showing its structure; and a whorl of united leaves, with part of a whorl of 

 branches. Natural size. 



Fia. 109. — A^ part of an old con^ of the Great Horsetail, showing three sepa^ 

 rated whorls of shield-shaped leaves; B, three shield-shaped leaves, slightly 

 magnified; st, stalls, and s, expanded part of leaf; ag, the spore-cases. 



412. The fibro-vascular bundles of the stem are disposed 

 in a circle, and run parallel with each other from node to 



