38 On Hyhridisatioii of some Species o/Salix 



the former. All F^ plants are at first exactly similar to 8. gracilistyla 

 in this respect, so that the spreading habit may then be considered to 

 be dominant to the erect, but as the tree becomes older many branches 

 which are directed upwards are produced as in S, multinervis, thus 

 these older plants have become intermediate between the two parents. 

 From these F^ plants I obtained 442 in the F^ generation, of which 224 

 are spreading and 218 erect. The fact that the erect habit is a pure 

 recessive character against the spreading has been also proven in the 

 following way : I fertilised an extracted erect F2 'plant by the original 

 erect parent (= S. multinervis), and found the offspring, numbering 89 in 

 all, to be erect without exception. The segregation of the characters 

 under consideration in F2 generation has thus been clearly shewn, but 

 the ratio of the two kinds of plants is very different from what we 

 might have expected had this segregation taken place in the usual 

 Mendelian fashion. 



(b) Hairiness of Leaves. 



In >S^. multinervis the leaves are quite glabrous on both surfaces, 

 whilst in 8. gracilistyla they are at first hairy on both surfaces, and 

 throughout their life on the lower, being more or less densely covered 

 with long gray hairs, especially along the veins. Leaves of F^ plants 

 resemble the former entirely in this respect, because they are perfectly 

 glabrous on both surfaces, so that the non-hairiness may be considered 

 to be dominant to the hairiness ^ In the F^, generation I got 425 plants 

 in all, of which 35 1 have perfectly glabrous leaves like the one parent, 

 and 74 leaves more or less hairy underneath like the other. It may 

 here be remarked that among the hairy leaves the degree of hairiness 

 is very different in different individuals, and that I was unable to find 

 even a single plant which is so densely hairy as in the one parent, 

 S. gracilistyla. This is perhaps due to the fact that we have here a 

 large number of factors concerned in the hair-production, and it seems 

 not unlikely that the cultivation of a much larger number of F^ plants 

 may give rise to a certain number of such leaves which are as hairy as 

 in >S'. gracilistyla. 



In respect to the character "hairiness of leaves" I will mention 

 here the hybrid between S. m.ultinervis and S. viminalis^ The former 

 has quite glabrous leaves as above stated, while the latter, which is 

 found here as well as in Europe, has, as is well known, leaves very 



1 Some of the inner leaves in buds, and sometimes a few very small ones crowded 

 together at the base of young branches, are more or less hairy. 



