JOURNAL 



OF THE 



ARNOLD ARBORETUM 



Volume I JANUARY, 1920 Numbeb 3 



NOTES ON AMERICAN WILLOWS. VII 



Camillo Schneider 

 a. THE SPECIES OF THE SECTION ADENOPHYLLAE 



This section consists of two main types of which one is characterized by 

 the more or less bluish white undersurface of the leaves while the other has 

 the leaves greenish beneath, I do not, however, wish to say that the species 

 with discolor leaves are to be regarded as more closely related to each other 

 than to the species of the other group. It is, at present, very difficult to 

 Judge the true relationship of the different forms referred by me to this 

 section. Furthermore, it is by no means easy to separate this group from 

 the section Cordatae or from other species of diflFerent sections. As to the 

 Cordatae, I am not yet well enough acquainted with some of the western 

 forms of this group to be able to draw a sharp line between them and the 

 Adenophyllae, I think, however, that the structure of the stigma and the 

 style combined witli other peculiarities of the flowers are the best characters 

 by which to separate those two sections, I hope to point out these charac- 

 ters more clearly in the keys which I shall prepare for all the American 



species, 



A very remarkable species is S, Chamissonis, which I refer only provi- 

 sionally to this section. The characters of Its flowers are very similar to 

 those of the other species but the habit and the leaves distinguish It at the 

 first glance from them. Salix adenophyUay the type of this section, seems to 

 be closely related to S- commutata and S. Easiwoodiaey but it Is a well-marked 

 species. The last two species are rather diflScult to separate, and *S. com- 

 mutata may be connected with *S. Barclayi by certain forms which need fur- 

 ther study. There are, besides, hybrids between the two species, and I 

 suppose that a better understanding of the variability of both species will 

 enable us to distinguish other varieties or even subspecies. With S. Bar- 

 clayi seems to be very closely connected a form from Alaska named by Co- 



Walpolei I] 

 ae because 



form 



at Washington and I regret that the name has not yet been published. For 

 this reason I am not able to deal with this variety or species. There is an- 

 other form collected bv Miss Eastwood in the Yukon TerrItor\^ and north- 



