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.) 



more or less branched. Abnormal forms are not un- 

 common in which the fertile spike is more or less steril- 



