280 DIOECIOUS AND Chap. VII. 



This, howev&r, would be effected only under the con- 

 tingency of a reduced number of seeds, produced by 

 the females alone, being sufficient to keep up the 

 stock. 



There is another way of looking at the subject which 

 partially removes a difficulty that appears at first sight 

 insuperable, namely, that during the conversion of an 

 hermaphrodite into a dioecious plant, the male organs 

 must abort in some individuals and the female organs 

 in others. Yet as all are exposed to the same con- 

 ditions, it might have been expected that those 

 which varied would tend to vary in the same man- 

 ner. As a general rule only a few individuals of a 

 species vary simultaneously in the same manner ; and 

 there is no improbability in the assumption that 

 some few individuals might produce larger seeds 

 than the average, better stocked with nourishment. If 

 the production of such seeds were highly beneficial to 

 a species, and on this head there can be little doubt,* 

 the variety with the large seeds would tend to in- 

 crease. But in accordance with the law of compensa- 

 tion we might expect that the individuals which pro- 

 duced such seeds would, if living under severe con- 

 ditions, tend to produce less and less pollen, so that 

 their anthers would be reduced in size and might ulti- 

 mately become rudimentary. This view occurred to 

 me owing to a statement by Sir J. E. Smith f that 

 there are female and hermaphrodite plants of Serratula 

 tiwtoria, and that the seeds of the former are larger 

 than those of the hermaphrodite form. It may also 

 be worth while to recall the case of the mid-styled 

 form of Lyihrum salicaria, which produces a larger 



* See the facts given in ' The f ' Trans. Linn. Soo.,' vol. xiii. 



Eifeots of Cross and Sell-fertilisa- p. 600. 

 tion,' p. 353. 



