EQUISETUM. 247 



and from buds organized at the same points arise the aerial 

 stems. These are quite dissimilar in their appearance, some 

 being short, quite simple, and terminating in a cone-like 

 head of spore-cases; others being without fructification, 

 taller, and producing several whorls of long, crowded, slen- 

 der branches ; whilst a third kind, of ' common though not 

 constant occurrence/ produce whorls of branches and cones 

 also. In the production of these three kinds of stems it 

 serves to connect, through E. sylvaticum, that group in 

 which the fertile and barren stems are successive and alto- 

 gether unlike, with that in which any of the stems indif- 

 ferently at least as to external appearances bear the fruc- 

 tification, all being of similar habit. 



The fertile stems grow about six inches high, and are 

 quite branchless ; they are of a pale yellowish-green, having 

 numerous joints, the large loose funnel-shaped sheaths pro- 

 duced at these points, almost covering the stem, as usually 

 described and figured, but in our specimens they are much 

 less crowded, a space of from half an inch to an inch oc- 

 curring between the adjoining sheaths. These sheaths are 

 still paler- coloured than the stem, often almost white, with a 

 dark ring below the teeth, which are awl-shaped, pale brown, 

 with pale-coloured membranous margins; the teeth are 



