EQUISETUM. 249 



when in a Inxuariant condition of growth. They grow 

 erect, and are from six to seven feet or more in height, 

 clothed nearly to the bottom with spreading proximate 

 whorls, those on the stouter parts consisting of thirty to 

 forty branches, which are sometimes again branched. The 

 upper whorls have a less number of branches. The whorls are 

 most crowded towards the top of the stem, and there also 

 the branches are about the full length — six or eight inches ; 

 lower down the stem the branches become shorter, and 

 the whorls more distant. The stems measure about 

 an inch and a half in diameter at the stoutest part, and 

 from this point decrease upwards, becoming very slender at 

 the point. The surface is smooth, with mere indications 

 of about thirty faint lines extending into the sheaths, and 

 there becoming more apparent. The sheaths set close to 

 the stem, or nearly so, and are half an inch long, green 

 below, with a dark brown ring at top, and divided at the 

 margin into slender bristly teeth, about half an inch long, 

 dark brown, with paler membranous edges ; the teeth fre- 

 quently adhere together in twos and threes. The branches 

 have eight or ten ribs united in pairs, and their sheaths 

 terminate in four or five teeth, each extended into a slen- 

 der black bristle, and having two denticulated ribs. The 



