IOWA ACADEMY OF SCIENCES. 149 



Granite, Lyon Co. 1, Shimek, S. U. I,; Mason Olty, Oerro Gordo Oo. 11, SMmek, S. U, I.; 

 Nora Junction, Floyd Oo. 13, Shimek, S. t7. 1.; Charles Olty, Floyd Co. li, Arthur (Engelm, 

 Herb. Mo. Bot. Oarden); Dakota Olty, Humboldt Co. 16, Stewart; Fayette, Fayette Oo. 18. 

 Fink. Herb. (2 spec.'*; Delaware Co. 23, Cameron, S, U.I.; Dubuque. 34, Th. Engelmann 

 (Engelm. Herb. Mo. Bot. Oard.); Gilbert, Story Co. 27, Pammel and Beyer {No. 1202) ; Ames 

 Story Co. 38, Bessey, Hitchcock (2 spec). Ball and Sample (No. 119S), Pammel and Ball (No. 

 ii99);Iowa City, .lohnson Oo. 36, Under S. [7. Z. ; Davenport. 39, AfiJler (No. 1200); Mus- 

 catine. 41, Reppert (Nos. 452, viii, and one other); Carson, Pottawattamie Co. 43, Cameron, 

 S. Z7. 1. ; Mt. Pleasant. Henry Co. 44, Mills, Herb.; Steamboat Rock, Pammel & Hume. 

 (No8. 1930 A, 1931 B, 1935 F, 1947 Q) , No. 1931 B approaches S. tristis. 



VIII. SALIX TRISTIS AIT. 



Salix tristis Ait. Hort. Kew. 3: 393. 1789. 



This dwarf willow is very much like the preceding species 

 and has the same general range but is nowhere as common as 

 its larger relative. The leaves are smaller and rather densely 

 clustered. The aments are smaller (one-fourth to one-half 

 inch) and fewer — usually about twenty-flowered. The height 

 is given as from one to two feet but there is no hard and fast 

 line of demarcation between the two species. A favorite loca- 

 tion for this willow is the border of hillside thickets. Flowering 

 period as in S. humilis. 



Webster City, Hamilton Co. 21, Stewart; " Ledges", Boone Co. 25, Pammel (No. 1201); 

 Harrison Oo. 34, Burgess; Johnson Co. 36. Shimek, S. U. I. (2 spec.) 



IX. SALIX SERICEA MARSH. 



Salix sericea Marsh. Arb. Am. 140. 1785. 



This species is quite rare in Iowa. According to Mr. Bebb 

 it occurs commonly as far west as the great lakes, but from 

 there westward is largely replaced by S. petiolaris. Granting 

 this to be the fact, we would expect to find a strip of territory, 

 where their ranges overlap, in which the two species would be 

 present in about equal quantities. But as far west as Iowa 

 we would expect to find S. sericea much less common than its 

 western representative, S. petiolaris. This is exactly what 

 occurs. S. sericea is recorded for Iowa from but three local- 

 ities, all in the eastern part of the state. 



There is considerable difficulty in differentiating these two 

 species. However, if the specimen includes either fruit or 

 mature foliage the task is not so difficult. Both species are 

 said to hybridize freely with S. cordata, which increases the 

 confusion of forms very considerably. The twigs of S. sericea 

 are reddish or yellowish, deepening to purplish. The leaves 

 are lanceolate, two to three inches long by one-half inch wide, 

 densely silky when young and usually retaining part of this 

 pubescence when mature, at least on the lower surface, which 



