354 



Salicaceae 



Salix 



o ~T6 

 Map 732 



Populus tremuloides Michx. 



50 



Map 733 



Salix nigra Marsh. 



~~ 30 



Map 734 



Salix amygdaloides Anders. 



5. Populus grandidentata Michx. Largetooth Aspen. Map 731. This 

 is a tree of small or medium size found more or less frequently in the 

 lake area and less frequently in the unglaciated area. Outside these areas 

 it is local or absent. In the northern part of the state it is found in low- 

 ground while in the unglaciated area it is usually found on the crests of 

 the highest ridges. 



N. B. to Minn., southw. in the mts. to S. C, Ohio, Ind., and Iowa. 



6. Populus tremuloides Michx. ASPEN. Map 732. This small tree is 

 common in low ground in the lake area and I have never seen it growing 

 on hills. It has been reported from all parts of the state but all of the speci- 

 mens I have seen from the southern part of the state should be referred 

 to the preceding species. It is doubtful whether it occurs far south of the 

 stations shown on the map, and, if so, it will be found very locally. 



Newf. and Lab. to Alaska, southw. to Term., Mo., Nebr., and in the mts. 

 to Mex. and Calif. 



1873. SALIX [Tourn.] L. Willow 



Note: Specimens of this genus are difficult to determine because the 

 species are dioecious, are highly variable, and freely hybridize. Hence it is 

 advisable to collect a flowering specimen and later to collect a mature leaf 

 specimen from the same plant to make determination easy and certain. 



KEY BASED PRIMARILY ON PISTILLATE FLOWERS AND CAPSULES 



Ovary glabrous; bracts of flowers usually deciduous before maturity of the capsule. 

 Ovary sessile or subsessile. 



Leaves cordate at the base, silky-pubescent above 17. S. adenophylla. 



Leaves cuneate at the base. 



Blades more or less pubescent at flowering time; capsules 3-5 mm long. 6. S. alba. 



Blades usually glabrous at flowering time; branches pendulous; capsules 1.5-2 



mm long. (See excluded species no. 162, p. 1038.) S. babylonica. 



