46 Oil Hfjhrldisation of some Species o/Salix 



really heterozygous in this respect ? For the elucidation of this question 

 I have made the fertilisation between male and female trees of each of 

 the two species — the very same trees which were used in my hybridisa- 

 tion experiments ; this fertilisation might correspond to selfing in 

 hermaphrodites. Seeds obtained by this process were sown, and plants 

 developed from them — 70 in S. gracilistyla and more than 100 in 

 S. multinervis — and were found to be exactly similar to their respective 

 parents in all respects. There is therefore no reason for considering 

 either of the two parents to be heterozygous regarding the catkin 

 character under consideration, and the first hypothesis should be dis- 

 carded. 



According to the second hypothesis one sex, either male or female, 

 of one of the two species, is regarded as heterozygous and the other 

 homozygous in respect to the catkin character. Thus suppose, for 

 instance, the male plant of >S^. gracilisti/la to have the formula Gg, and 

 the female GG, then the fertilisation between them which is a back- 

 cross gives Gg ^ and GG J , and as G is dominant over g, S. gracilistyla 

 breeds always true despite the heterozygous nature of its male plant. 

 The hybridisation of gg $ (= S. multinervis) by Gg ^ (= S. gracilistyla) 

 should give in F^ the zygotes represented by Gg and gg, but as the 

 female G-type plant should be always homozygous (= GG) according 

 to our presupposition, we should have in F^ 



thus not one female G^-typed plant should then appear, which is 

 contrary to the fact actually seen, because I obtained seven female 

 (r-type plants (p. 42). 



What will be the case, if we suppose the presence of the inhibitory 

 factor of hairs I ? Thus, for example, suppose the male plant of 

 S. multinervis = W, its female plant = li, >S'. gracilistyla (both male and 

 female) = ii, then the hybridisation li J x li ^ gives in F^ 11 and ii, and 

 since, according to our presupposition, the male if-type plant should 

 be always homozygous (= II) we should have in F^ 



li ¥ +il J+iic/', 



thus not one male i/-typed plant should appear, which indeed accords 

 with the fact, for I got no such plant in F^ (p. 42). The F.^ offspring 

 arising from the fertilisation between male and female (?-type F^ 

 plants (i.e. ii?xii(/=ii?+ii^) should however undergo in F^ no 

 segregation, and give G-type plants exclusively, which is contrary to 



