Roscndahl: observations on betula 451 



bract, samara and leaf to disprove this assumption, it seems justifi- 

 able enough. However, the question can not be said to be settled 

 until actual crossing has been carried out under control. 



Winkler, in the preparation of the above-mentioned monograph, 

 had under observation some specimens loaned him by Schneider 

 and Zabel, one of which he surmises to be a cross between B. lutea 

 and B. piimila. Apparently he felt that the material was insuffi- 

 cient or that there were not conclusive data enough at hand, other- 

 wise it seems he would have described it and included it among the 

 rest of the hybrids diagnosed. 



Two years later, however, Schneider^ described such a hybrid 

 and stated it to have been obtained from Michigan by Purpus of 

 Darmstadt, the latter's brother having sent it to him from Clark's 

 Lake. It is named B. Purpusi and is described as a shrubby plant 

 of the pumila form and is further characterized as var. typica, to 

 distinguish it from a tree-like plant growing in the Darmstadt 

 garden, apparently raised from seed from the Michigan plant by 

 Purpus. This Darmstadt plant is designated var. luteoides. 



Whether or not these forms are identical with the Minnesota 

 material, only actual comparisons of specimens can show, for de- 

 scriptions alone are not adequate in such cases. Unfortunately, on 

 account of the present European upheaval, the exchange of ma- 

 terial is out of the question, and it must remain for the future to 

 settle these points. 



A hybrid between B. lent a and B. pumila has also been known 

 for some time, being described by Jack in Garden and Forest in 

 1895. This plant was grown in the Arnold Arboretum and bears a 

 close general resemblance to the B. lutea x pumila var. glandulifera 

 hybrid, as would naturally be expected. The characters of fruiting 

 catkin, bract and samara are sufficiently distinct, however, to sep- 

 arate them without any difficulty. 



Since none of these hybrids seem to have been observed in the 

 field to any extent outside of Minnesota, possibly because they may 

 be more or less easily confused with young specimens of one or the 

 other of the parent species, it seems desirable to add to what has 

 already been said, an analytical key to all the hybrids and the parent 

 species, and in addition brief diagnostic descriptions of the former. 



« Illustriertes Handbuch der Laubholzkunde. 1, 102-103. 



