444 MINNESOTA BOTANICAL STUDIES 



versity collection, except one by Sandberg, could possibly be referred 

 to Britton's species. Considering the fact that Hennepin County, in 

 which the birch had been first collected, has been more thoroughly 

 studied than any other in the state, it seemed remarkable that a 

 species, apparently so well marked, could have escaped notice com- 

 pletely for so long a time. A systematic attempt was therefore made 

 to rediscover the plant, not, however, with much hope of early suc- 

 cess, for it seemed that if at all common, it surely would have been 

 encountered during the long intervening period. Furthermore, the 

 indefinite legend, "Swamps, Hennepin County," which characterized 

 Sandberg's collection, furnished no helpful clue, for Hennepin 

 County is a part of Minnesota which is literally dotted with swamps. 

 However, on a field trip early in September, 1911, a birch was found 

 in a swamp near the middle of Hennepin County, which at once 

 proved to be different from any of the common and well-known 

 species of the state. It happened to be in excellent fruiting condi- 

 tion and ample material was secured. 



One thing about the new material was, however, disconcerting. 

 It did not resemble very closely Sandberg's collection in the Univer- 

 sity Herbarium, which some time subsequent to 1904 had been 

 designated "Cotype" and was therefore taken to be authoritative. 

 On the other hand, it seemed to agree admirably with Britton's de- 

 scription. Obviously there was a discrepancy of some kind and it 

 seemed that the quickest way to straighten out the difficulty would 

 be to compare both Sandberg's specimen and the recent collection 

 with the type material. The two collections were accordingly sent 

 to the New York Botanic Garden where Dr. Rydberg kindly made 

 the comparison. The new material was stated to be "almost identi- 

 cal with the type specimen of B. Sandbergi except that the latter is 

 a little more pubescent" and further that "there is no difference in 

 the bracts of the catkins nor in the winged fruits. The mounted 

 specimen collected by Sandberg differs only in the broader leaves 

 and the thicker catkin, but those catkins are not broader than the 

 catkins of some specimens collected by Mr. Butler in Montana and 

 referred to B. Sandbergi by him." 



The authenticity of the new collection was therefore fully enough 

 established. About the Sandberg specimen there might be some 

 slight doubt, although the larger size of the catkins and the greater 

 width of leaf are insufficient to warrant separating it from the other. 



During the spring following the rediscovery of B. Sandbergi 



