ii6 MENDELISM chap. 



repulsion between the factors more intense (cf. p. 127) 

 we should obtain an Fg generation consisting 

 practically entirely of three classes, viz. males, 

 females, and hermaphrodites, which always gave the 

 three forms, male, female, and hermaphrodite in 

 the ratio 1:1:2. In such cases the true breed- 

 ing hermaphrodite and the sexless forms would 

 appear only as extreme rarities. 



We have instanced this case of the sweet- pea 

 to illustrate how complex a thing sex in plants 

 may be, and how little understood at present. It 

 is not improbable that it may be organised on 

 different lines from those with which we are becoming 

 familiar in animals, but, until we have a far greater 

 body of facts to guide us, speculative interpretations 

 have merely a suggestive value. Up to the present 

 the cytologists have not provided us with any 

 evidence of sex -chromosomes in plants. There is, 

 however, an experiment of Baur with the common 

 Lychnis, a plant with separate sexes, which seems 

 to show that sex-limited inheritance may also occur 

 in the vegetable world. 



A male individual with narrow leaves was found 

 growing wild. Crossed with a broad-leaved female 

 it gave progeny of both sexes with broad leaves 

 only. In F^ the narrow-leafed form reappeared 

 as a recessive. All of them, however, were males, 

 though both sexes occurred among the broad- 

 leaved forms. Further experiments by Shull have 

 revealed complications in connection with the 

 proportions of the sexes, and it cannot be said 

 that the case is yet fully understood. Nevertheless, 

 the similarity of Baur's results to those obtained 



