458 MINNESOTA BOTANICAL STUDIES 



a grouij of the parent jjlants. It resembles the hybrid between B. 

 liitea and B. piimila var. glandiilifera somewhat closely but can be 

 distinguished by the more reddish bark of the branches, more 

 pubescent young twigs and leaves, the absence of resin glands on 

 the leaves and twigs, and by the nearly or quite glabrous bracts. 

 The dense pubescence of the eastern hybrid and the lack of glands 

 upon the herbage are to be ascribed to the fact that the young twigs 

 and foliage of typical B. piimila of the east are mostly downy 

 pubescent and not at all glandular. 



Betula pumila var. glandulifera Regal Bull. Soc. Nat. Moscou. 



38:41. 1865. 

 B. glandulifera ( Kegel j Butler, Bull. Torr. Bot. Club, 36. 1909. 



The typical B. pumila of eastern North America does not appear 

 to occur w^ithin the boundaries of Minnesota, although credited to 

 the state in reports and manuals. 



The form which is found nearly everywhere in our tamarack 

 swamps and bogs from the southern to the northern boundaries of 

 the state is the variety glandulifera. The young branches are always 

 more or less glandular dotted, mostly puberulent and sometimes 

 with a few scattered, long hairs, but never woolly pubescent as in 

 the eastern representatives of the species. The foliage is nearly 

 always glandular and glabrous throughout, or at most only thinly 

 pubescent when young but soon becoming smooth all over. Some- 

 times a few scattered hairs remain on mature leaves towards the 

 base and on the puberulent petioles. In form the leaves vary from 

 broadly obovate to wedge-obovate, and are crenate-serrate to 

 coarsely dentate. Some specimens from the Lake of the Woods 

 and the northwestern corner of the state are more densely glandu- 

 lar-dotted on the young twigs than specimens from other parts of 

 the state and seem to occupy an intermediate position between B. 

 pumila var. glandulifera and B. glandulosa. There are, however, 

 no collections of the latter species from iMinnesota in the Univer- 

 sity Herbarium, and it is very doubtful if it reaches the state al- 

 though it has been so reported. 



