725 



generally of an ebony blackness, and seems to spread with considera- 

 ble rapidity, so that when once introduced a large patch is soon formed. 



The stems are of three kinds, as in the preceding species ; firsts 

 bearing fructification only ; secondly, bearing both fructification and 

 branches ; and thirdly, bearing branches only. The exclusively fer- 

 tile stems come up in March, shed their seed in April, and disappear 

 in May : the figure on the opposite page represents a fertile stem 

 of the natural size and proportions, but divided for more conveni- 

 ent representation : it is nine inches in length, and has six joints, se- 

 veral shorter and subterranean ones having served to unite it with the 

 rhizoma. I have, in some instances, found the total number of joints 

 to be fifteen ; the stem, scarcely observable, owing to the great length 

 of the sheaths, is pale brown, smooth and succulent. The sheaths are 

 very large, loose and spreading towards the summit, distinctly stri- 

 ated, and terminate in from thirty to forty long, slightly flexuous, se- 

 tiform teeth ; the sheaths at the base are pale brown, but are much 

 darker towards the summit. The catkin is about two inches and a 

 half in length, and at length an inch and a half in circumference : the 

 scales are very numerous, often reaching four hundred in number ; 

 they are arranged in whorls, of which the lower ones are always suf- 

 ficiently obvious. 



When the stem bears both fructification and branches, it is seldom 

 in perfection until the month of August : such stems are far less nu- 

 merous than in either of the preceding species, and bear but a small 

 proportion to those which are exclusively fertile or exclusively bar- 

 ren : the catkin is much smaller than under ordinary circumstances : 

 the stem also is smaller, although having longer joints ; the sheaths 

 are shorter, less spreading, and of a pale green colour ; the branches 

 are placed on the second to the ninth or tenth joint, counting from 

 the catkin ; in all the specimens I have seen they are ascending. 



The barren stem is much larger than in any other species of Equi- 

 setum with which I am acquainted : it occasionally attains a height 

 of seven feet, and a circumference of more than two inches ; its out- 

 line and proportions are shown, on a very reduced scale, at page 721, 

 fig. a, and one of the internodes, with its accompanying sheaths, is 

 represented of the natural size at fig. h. 



The following is the description of a living stem now before me, of 

 the average size. The entire length above ground, and including the 

 ascending branches, is fifty-four inches ; the circumference, at twelve 

 inches from the ground, is an inch and a half, but decreases upwards 

 until it becomes extremely slender, terminating almost in a point. 



