JOURNAL 



OF THE 



ARNOLD ARBORETUM 



Volume I 



OCTOBER, 1919 Number 2 



NOTES ON AMERICAN WILLOWS. VI. 



Camillo Schneider 



a. THE SPECIES OF THE SECTION PIIYEICIFOLTAE 



The following study of the species of the section Phylicifoliae is cluefly 

 based on the collections of the herbaria of the Arnold Arboretnm, the Field 

 Museum of Chicago, the Californian Academy, the Missouri Botanic 

 Garden, the Geological Survey of Canada, the Leland Stanford University, 

 of Professor W. L. Jepson, Berkeley, Cal., and of the Gray Herbarium and 

 the National Herbarium, but I have been able to consult also some types 

 from the Kew Herl)arium and some specimens from the herbaria of the Uni- 

 versity of Washington and of the University of Wyoming. My thanks are 



due to the gentlemen in charge of these collections. 



ifol 



for the group to which I refer the following species. I have dealt with the 

 forms of eastern Asia of this section in Sargent, PI. Wils. in. 122 (191G). 

 To the synonyms there given is to be added: Sect. Argentcac Ball in Coulter 

 & Nelson, New Man. Rocky Mts. Bot. 136 (1909), non Koch, and sect. 

 Argentea Rydberg, Fl. Rocky Mts. 189 (1917), pro parte. Even if we 

 should place S. pclUta and the other species with permanently hairy leaves 

 in a different section, the name Argenieae used by Ball could, in my opin- 

 ion, not be adopted because the American spec'es cannot be united with 

 those forms which have been referred by Koch (De Salic. Comm. 46. [1828]) 

 to his section Argcnteae for which the oldest name is sect. Incuhaccae Dumor- 

 tier (Fl. Belg. Prodr. 12 [1827]). Rydberg's Argentea group is a mixture 

 of forms of very different relationship. He proposed, in 1906 (Fl. Colo. 93) 

 a sect. PeUitae, and it might be the best to use this name for our group if a 

 more thorough study of the relationship of the different sections should 

 prove that the American forms of the Phylicifoliae are more closely related 

 to each other than to the species of the Old World. 



I am doubtful whether a species like S. pulchra Chamisso should be in- 

 cluded in this section. It seems to me that it may have closer relations 

 with S. Richardsonii Hooker and its allies. But, of course, that is a ques- 

 tion which only can be decided if one is better acquainted with all these 

 forms than I am at present. S. pulchra differs from the other species of this 

 section by its well- developed and more or less persistent stipules. 



