HETEROSTYLISM. 215 



legitimately fertilised heteromorphic unions in fertility. 

 Thus, Mr. Darwin observes, "The self -fertility of Primula 

 veris increased after several generations of illegitimate fertili- 

 sation, which is a process closely analogous to self -fertilisa- 

 tion." * 



Lastly, if homomorphic forms occur spontaneously, as is 

 often the case with species of Primula, Mr. Darwin has 

 shown they are not only " capable of spontaneous legitimate 

 fertilisation, but are rather more productive than ordinary 

 flowers legitimately fertilised." f 



It was Mr. Scott who suggested that the equal-styled 

 varieties arose through reversion to a former homostyled 

 condition of the genus. Mr. Darwin supported this view in 

 consequence of observing " the remarkable fidelity with which 

 the equal-styled variation is transmitted after it has once 

 appeared." J 



* Cross and Self Fertilisation, p. 351. 



t Forms of Floiuers, p. 273; and Cross and Self Fertilisation, p. 352. 



X Forms, etc., p. 274; Mr. Darwin was so profoundly impressed wdth 

 the supposed advantages of intercrossing, that he again and again 

 asserts most positively that self-fertilisation is injurious, often in 

 diametrical opposition to his own statements and experiments. Thus, 

 while speaking of heterostyled trimorphic plants, he says, " As I have 

 elsewhere shown (The Effects of Cross, etc.), most plants, when fertilise(5 

 •with their own pollen, or that from the same plant, are in some degree 

 sterile, and the seedlings raised from such unions are likewise in some 

 degree sterile, dwarfed, and feeble." Yet, in the work quoted, he has 

 not only shown that, when he persevered with self-fertilisation for several 

 generations, he found it was just the reverse; as e.g. with "Hero" Ipomceat 

 the white Mimulus, etc., and with Primula, as stated above ; but he 

 more than once draws an opposite conclusion, as when speaking of self- 

 fertile varieties (I.e., p. 352): *'It is difficult to avoid the suspicion 

 that self-fertilisation is in some respects advantageous. . . . Should this 

 suspicion be hereafter verified, it would throw light on the existence [of 

 cleistogamy]." It is this " suspicion " which I have completely veri- 

 fied ; and, indeed, any idea of " injuriousness " is refuted by the majority 



