36 On Hyhridisation of some Species of Salix 



abundant quantity of pollen, the large majority of ovaries did not come 

 to maturity, and I got only a few good seeds, which have given rise to 

 fourteen jPi-individuals. In 1911 the same hybridisation was repeated 

 on the same female tree used in 1910, and I got almost fifty seedlings. 

 The result of the latter hybridisation was entirely different from that 

 in 1910, as described later in this paper (p. 51 ff.). The reciprocal 

 hybridisation was not done in 1910, for the female plant of 8. gracilistyla 

 was not then available in our Botanical Garden. That year however 

 I brought some branches of its female plant from a wild growing 

 locality, some twenty miles away from Tokyo ; they were cultivated as 

 cuttings, and came to flowering in 1912. One of these female individuals 

 was hybridised in 1912 with the male plant of >S^. multiyiervis. This 

 hybridisation failed, and nq ripe seeds were obtained. In 1 918 the two 

 reciprocal hybridisations were repeated, and as I was able to obtain a 

 certain number of seedlings from one of them, S. multinervis % x S. graci- 

 listyla </ , my experiments wdll, as far as possible, be continued on these 

 plants. The other, S. gi'acilistyla ^ x S multinervis c/" , failed again ; it 

 seems to be well-nigh impossible \ 



A. Results of the Hybridisations done in 1910. 



The fourteen individuals obtained as the result of the hybridisation 

 performed in 1910 began to flower in 1912, and were found to consist of 

 ten females and four males which show clearly the hybrid nature in 

 their vegetative organs as well as in their catkins. 



The corresponding characters of the two parents and the F^ plants 

 dealt with in this paper are as follows : 



S. mnltine7'vis. Stem and branches erect. Leaves glabrous on both 

 surfaces^ without stipules (cf Text-fig. 1 B). Catkin, either male or 

 female, sparingly hairy (Plate I, fig. 2 J^ — $ ). Stigma bright scarlet- 

 coloured. 



8. gracilistyla. Stem and branches spreading. Leaves hairy on 

 the lower surface, especially along mid- and side-veins, stipulate (cf. 



^ In both 1912 and 1918 a number of female catkins of *S'. gracilistyla were repeatedly 

 dusted with plenty of pollen of S. multinervis, yet only very few ovaries in each catkin (only 

 1 — 10 out of some 400 ones in one catkin) have swollen to a certain extent, and after a 

 few days all of these catkins have fallen off. In 1918 however only one catkin remained 

 on the tree, and some 10 small fruits on it came to open, but were found to contain a few 

 tiny seed-rudiments with seed-hairs normally developed. 



2 Except few, very young leaves yet inrolled in the bud, which are very sparingly 

 hairy. 



