THE AMERICAN NATURALIST [Vol. XLII 



upon cultivated crops seem sometimes to remain in the 

 soil without germination more than one season, and to 

 germinate when a new cultivated crop is planted. The 

 accompanying figure represents -the manner of germina- 

 tion of a member of group V and the growth of its flower 

 stem. 



Figs. 5 and 7 respectively represent two parasitic 

 plants which, although they originate from physically 

 similar embryos, are so widely different in their mature 

 structure and habits that the following comparison is 

 thought to be desirable. The seeds of both these parasites 

 germinate upon the ground, but the resulting plantlet 

 of one of them grows upward and that of the other down- 

 ward, in search of a host. The plantlet of Cuscuta grows 

 upward, which is attributed to the assumed fact that its 

 embryo possesses a considerable representation of the 

 apotropic portion of a normal plantlet, and little or 

 no representation of the epitropic portion. No part 

 of the broom-rape embryo grows upward, presumably 

 because it possesses no representation of the apotropic 

 portion of a normal embryo. Its whole embryo seems 

 to represent only a moiety of the stem of a normal 

 plantlet which lies subjacent to its tropaxis and above its 

 rootlets. The bud from which springs the flowering stalk 

 of broom-rape is not a part of the embryo proper, as is 

 the plumule of the normal embryo, but a result of sec- 

 ondary germination. 



Group VI 



Seeds germinate only above ground and, like those of 

 the mistletoes, only upon a living woody host; usually 

 upon the stem and branches, but sometimes upon exposed 



