176 STRUCTURE AND LIFE HISTORIES 
Botrychium usually (though not invariably) possess but 
one foliage-leaf, and a fertile spike, both of which are 
FIG. 133. Rattlesnake fern (Botrychium virginianum (L.) Sw.). 
more or less branched. Abnormal forms are not un- 
common in which the fertile spike is more or less steril- 
