436 PTERIDOPHYTES (FERN PLANTS) 
Sporophyte. — The sporophyte consists of a horizontal, much 
branched, underground stem from which two kinds of aérial 
branches or shoots arise (Fig. 390). One kind of shoot bears 
spores and is called a fertile shoot, while the other kind does only 
vegetative work and is called a sterile shoot. Both kinds of 
Fic. 390. — Equisetum arvense. A, a portion of the underground stem 
with two fertile or spore-bearing shoots, each of which bears a strobilus (d) 
(x 4). B,a portion of a sterile or vegetative shoot (x 4). C, asporophore, 
showing the stalk and umbrella-lite top on the under surface of which are the 
sporangia (e) (X 6). Below, at the right, are shown spores, one with elaters 
coiled about the spore and the other with elaters uncoiled (x about 15). 
shoots are formed under the ground in the fall in most Equise- 
tums and are thus ready to elongate and appear above ground 
early in the spring. On both kinds of shoots the leaves are mere 
scales, which are so joined as to form a sheath at each node. The 
sterile shoots produce whorls of slender branches at the nodes and 
are so finely branched as to resemble a horse’s tail — whence the 
name Horsetails. The food is made by the green cortex of the 
