248 THE STRUCTURE OF FLOWERS. 



plants appeared, and 700 female, in the thickly sown plot, 

 while only 70 males occurred when thinly sown. This has 

 been paralleled in America, where Mr. Meehan, of Phila- 

 delphia, has noticed how Amhrosia arte misisef alia, if growing 

 vigorously, has a proportion of female flowers largely in 

 excess of the males ; but in fields where the grain has been 

 cut, and this " Rag- weed " comes up in thick masses late in 

 the season, the individual plants nearly starving each other, 

 male flowers are very numerous, and some are wholly male. 

 Prantl also observed that the crowded prothallia of Ferns gave 

 rise to more antheridia, and scattered ones more pistillidia. 

 Pfeffer, too, noticed the same fact with Eqitiseium. 



. In these cases w^e seem to have results exactly the reverse 

 of those of the melon seeds : but while in the latter the male 

 flowers were accompanied by the precocious and excessive 

 vegetative energy, the female were prevented from appearing 

 at all ; for it must be remembered that normally male 

 flowers of melons appear before the females. In the case 

 of thin sowing, the . plants were in a natural and healthy 

 condition : but when crowded they were starved, and the 

 vital energy, being just enough to develop male flowers, 

 proved insufficient for the female ; and, conversely, when 

 thinly soTvm, "vitality" was not checked, and females were 

 abundant. 



The question arises, are all seeds potentially bisexual, 

 and one sex rather than another determined either by an 

 inherent vigorous constitution or by the conditions of the 

 environment during germination and growth ? or is there, so 

 to say, a determination of sex, or at least a predisposition, 

 at an earlier stage still ? Dr. Hoffman, judging from his 

 experiments, is inclined to the opinion that sex does not 

 reside in the seed, but depends on conditions of germination. 

 Mr. W. G. Smith arrived at the same conclusion, for he says 



