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Genus XXII. EQUISETUM, Linnaus. 



THE jointed tubular stems, and terminal cones of fructifica- 

 tion, are marks by which the Eguisetums may always be 

 readily distinguished from all other plants. The species are, 

 however, not so easily recognized among themselves, owing 

 to the great sameness which occurs among certain groups of 

 them. The chief features relied on for their discrimination, 

 are the similarity or otherwise of the fertile and barren stems, 

 the number of ridges or striae which occur on the exterior 

 surface of these sterns, and the structure of the sheaths 

 which surround the joints. By means of the peculiarities 

 which these parts present, the species may be certainly iden- 

 tified, and after a little experience has been had, several of 

 them may be at once known by means of those jprima facie 

 appearances, which it is probable will become associated 

 with the plants, in the mind of the attentive student. One 

 peculiarity of the Equisetums is, that they have no leaves, 

 these organs being represented by the tubular sheaths which 

 are produced at every joint. 



The name Equisetum is compounded from equus, a horse, 

 and seta, a hair or bristle ; whence comes the English name 



