CALAMITES AND LYCOPODS 369 



about 40 feet. In the island of Jamaica it is found in 

 thickets 10 to 15 feet high. 



334. Description of the Sporophyte. The plant body 

 (Fig. 267) consists of a horizontal, much-branched, under- 

 ground stem, or rhizome, from which spring two kinds of 

 sub-aerial branches sterile and fertile. The cells that 



FIG. 266. Equisetum fluviatik. Pure stand in shallow water, at Tully 

 Lake, N. Y. (Photo by W. L. Bray.) 



compose the sub-aerial branches are, in many of the 

 species (e.g. } E. arvense), nearly or quite all formed by the 

 close of the growing season, in the fall, so that in the 

 following spring all that is necessary is the expansion of 

 these cells, causing an elongation of the internodes and 

 the appearance of the branch above ground in early 

 spring. 

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