28 



HEREDITY AND EVOLUTION IN PLANTS 



ioglossum vulgatum, Fig. 28). The species of Botry- 

 chium usually (though not invariably) possess but one 



FIG. 27. Rattlesnake fern (Bolrychiitm virginianum (L.) Sw.). 



foliage-leaf, and a fertile spike, both of which are more or 

 less branched. Abnormal forms are not uncommon in 

 which the fertile spike is more or less sterilized, sometimes 



