46 THE HORSETAILS. 



buds at the top of the rootstock near the point where 

 the fertile stem arises. The sterile stems are much 

 taller than the fertile, in favourable circumstances reach- 

 ing a height of three feet. Ordinarily they are from ten 

 to fifteen inches high. The sheaths are shorter and nar- 

 rower than those of the fertile stems, but, like them, are 

 dilated upward. They are never so noticeable, being 

 usually pale green in colour and tipped with slender 

 dark-brown teeth. Toward the base of the stem the 

 entire sheath may be dark brown. 



In the section to which the field horsetail belongs, the 

 structure and number of grooves in the stem and the 

 arrangement of the sheaths play a less important part in 

 the identification of the species than they do in the 

 HippocJiczte. They are, however, not 

 without value for this purpose. In the 

 present species it may be noted that 

 there are eight or more leaves in the 

 sheath of the fertile stem, and about 

 fifteen in that of the sterile one. Since 

 there is usually one leaf for each groove 

 section of stem. o f the stem, the number of the latter 

 is easily ascertained. The tips of the leaves of this 

 species are not deciduous, and the central hollow of the 

 stem occupies about one third of its diameter. 



In what may be considered the normal plant, the stem 

 is erect and bears about twenty whorls of slender 

 branches, a whorl at each joint of the stem. Each whorl 

 consists of a dozen or more simple, three-angled, ascend- 

 ing branches six inches or more long, making a bushy 

 frond in which it is not difficult to fancy a likeness to 

 the tail of a horse. Doubtless it was the appearance of 

 this species that earned the common name for the 



