CHAPTER XI 
HORSETAILS AND CLUB-MOSSES 
HORSETAILS 
112. General characters.—The horsetails or equisetums 
are represented to- 
day by only twenty- 
five species; but 
during the Coal- 
measures the spe- 
cies were very nu- 
merous, and some 
of them were great 
trees, forming a 
conspicuous part of 
the forest vegeta- 
tion. They grow 
in moist or dry 
ground, sometimes 
in great abun- 
dance, and have 
such a character- 
istic appearance 
that they cannot 
be mistaken. 
The stem is slen- 
der and conspicu- 
ously jointed, the 
joints separating 
easily (Fig. 189). 
Bun 
Fic. 189.—Equisetum: showing the jointed and fluted 
stem, the sheath of minute leaves at each joint, 
strobili in various stages, and some young branches. 
197 
