34 On Hyh'idisation of some Species of Salix 



and hybrids^, it would not be without interest to study them from the 

 standpoint of modern genetical science. Thus very often the view 

 has been expressed that hybrids between various species of this genus 

 always breed true in later generations. The objects of my experiments, 

 which were begun in 1910 and continued till now, were to ascertain, 

 first whether segregation of characters takes place, and secondly whether 

 m this process, if it occurs, the Mendelian ratio can be detected. 

 As stated below, since willows come to flowering only in their third 

 year or even still later, the completion of the work will naturally 

 require a very large number of years, and if I continue it, I must 

 necessarily leave a very large space of my experiment-garden occupied by 

 hundreds of plants for a long duration of time. Thus, some inconclusive 

 results contained in this paper could not be brought to a definite end 

 without the cultivation of a considerably larger, number of plants, 

 perhaps ten times as many as those already raised. This is quite 

 impossible for the present author, who has only a small piece of land at 

 his disposal and has yet to perform there much other work. So it was 

 decided to discontinue the experiments on Salix, except as regards 

 certain points, and to publish the results so far obtained. Although, 

 as above noticed, the breeding experiments dealt with in this paper 

 were commenced in 1910 they contain many imperfections, and are 

 very far from being complete, so that this paper may be perhaps 

 regarded as a sort of preliminary communication. 



I. Methods of Investigations. 



Flowers of various species of Salix open in Tokyo generally at the 

 end of February and at the beginning of March, though in some, such 

 as >S^. Caprea, S. triandra var. nipponica, they open only at the end of 

 April. 



For the experiments of hybridisation male branches were cut off 

 and brought to a warm room, a few days before the opening of flowers, 

 and placed with their bases in a bottle full of water. When some 

 flowers began to open and to shed pollen I collected the latter in a Petri 

 dish by rubbing inflorescences with a hair pencil. As several days are 

 wanted for the opening of all flowers in one branch I repeated the 

 process every day till all flowers opened and began to shrivel. The 

 Petri dish with pollen was preserved in a cold, dark place. Pollen- 



1 Plunzeiilcben, Bd ii. 2 Ausg. 1905, p. 510. 



