42 



THE EVOLUTION OE SEX. 



more females, while males are more numerous in the country and 

 among the poor. 



(t) Determination of Sex in Plants. — It is at present extremely 

 difficult to come to any very satisfactory conclusion in regard to the 

 influence of nutrition upon the sex of plants. The whole subject, as far 

 as its literature is concerned, has been recently discussed by Heyer, 

 but his survey is by no means a sanguine one. His conclusions, in fact, 

 seem to land him in a skepticism as to all modification of the organism 

 by environmental influences, which we should of course be far from 

 sharing. It must be admitted that the experiments of Girou (1823), 

 Haberlandt (1869), and others, yielded no certain result; while the 

 conclusions of some others, are conflicting enough to justify not 

 indeed Heyer' s despair, but his present caution. Still a few inves- 

 tigations, especially those of Meehan (1878), which are essentially 

 corroborated by Diising (1883), go to show, for some cases, that 

 abundant moisture and nourishment do tend to produce females. 



Fig. 14. — Male and Female Flowers of Pink Campion (Lychnis diitrna). 



Some of Meehan's points are extremely instructive. Thus old branches 

 of conifers, overgrown and shaded by younger ones, produce only 

 male inflorescence. Various botanists, quoted by Heyer, confirm one 

 another in the observation that prothalho. of ferns grown in unfavor- 

 able nutritive conditions produce only antheridia (male organs), and 

 no archegonia or female organs. 



The botanical evidence, though by no means very strong, cer- 

 tainly corroborates the general result that good nourishment pro- 

 duces a preponderance of females. The contrast of the sexes in our 

 common diaecious plants is here very instructive. Taking, for 

 instance, the dog-mercury (Mercuria/is pcrennis) of any shady dell, 

 or the day-lychnis (L. diur?ia'), so often hardly less abundant on its 

 sunnier slopes, experiments are still certainly wanting with regard to 

 given plants as to what circumstances originally determined their 



