JOURNAL 



OF THE 



ARNOLD ARBORETUM 



Volume I JULY, 1019 Ncmbeu 1 



NOTES ON AMERICAN WILLOWS. V 



THE SPECIES OF THE PLEONANDRAE GROUP ^ 



Camillo Schneider 



In my conspectus of the Mexican si)ecies of Salix (Bot. Gaz. lxv. 1-41. 

 1918) I stated that I had " already made a rather extensive investigation of 

 the forms belonging to the Pleiandrae ^ group (sect. Nigrae, Triandrae, 



J 



Pentandrae subsect. Lucidae and Bonplandianae) "; I then dealt with all 

 the forms of this group which are found from Mexico to South America. 

 To-day I propose to give a key for the determination of all the American 

 species and varieties of these sections, to discuss their geographical distribu- 

 tion, and to deal with those forms of which I have not yet spoken in my 

 paper cited above. The Pleonandrac group is well defined in so far as the 

 male j)lants always have more than 2 (from 3 to 15) stamens, while all the 

 other American Salix (except of course some hybrids) have 2 stamens or 

 only one in S. sitchensis, S. Coulteri and S, Uva- Ursi. 



Besides the rich material of the her})arium of the Arnold Arboretum I 

 have been able to study the collections of the Gray Herbarium and of the 



M 



Lcland 



have had at my disposal part of the collections of the herbaria at Kcw, 

 New York, Reno and Washington.^ I wish to express my best thanks to 



^ The preceding parts of this series have appeared in Botanical Gazette: I. The species re- 

 lated to SaHx arctica Pall. (Bot. Gaz. lxvi. 117-14«. 1918.) — II. The species related to Salix 

 glauca- (1. c. 318-353. 1918.) — IIL A conspectus of American species and varieties of sections 

 Reticulatae, Ilerbaceae, Ovalifoliae and (ilaucae. (1. c. lxvii. 27-64. 19l9.) — IV. The species 

 and varieties of section Longifoliae. 0- <-'• 309-310. 1919.) See also A conspectus of Mexican, 

 West Indian, Central and South American species and varieties of Salix. (Bot. Gaz. lxv. 1-41. 



1918.) 



2 The name Pleiandrae was used by Andkrsson (18G7, 1868) but he included in his group 



also sect. Fragilcs of which the male plants are diandrous. I prefer to use the spelling Pleon- 

 andrac of von Seemen (Salic. Japon. 15. 1903) who restricts his group to the species with 



more than 2 stamens. 



* In the enumeration of specimens I am using the following abbreviations: A., Herbarium 

 of the Arnold Arboretum. — C, Herbarium of the Field Museum, Chicago. — Cab, Herba- 

 rium of California Academy of Science. — Cor., Herbarium of Cornell L'nivcrsity. — CU.. 

 Herbarium of University of Chicago. — E., Herbarium of the University of Oregon, Eugene. 

 G., Gray Herbarium. — Jeps., Herbarium of Professor W. L. Jepson, Berkeley, Cal. — K., 

 Kew Herbarium. — L., Herbarium of the University of Wyoming, Laramie. Wyo, — M., 

 Herbarium of the Missouri Botanic Garden. — N., Herbarium of the New York Botanic Gar- 



