454 MINNKSOTA BOTANICAL STUDIES 



largest birch trees noted in the state by the writer, occur here and 

 are mainly this variety. They differ from the ordinary forms of 

 the species, as it occurs in other parts of the state, by the more 

 yellowish tinge of the papery bark and more erect and solitary 

 habit of growth. The ri])e catkins attain a length of 5 to 6 cm. and a 

 diameter of 10 to 11 mm. ; the nutlet is usually about 0.5 mm. longer 

 than the average of B. papyrifera while the styles are mostly twice 

 as long or about 2 mm. In the original description Regel cites a 

 specimen from Pic River, Lake Superior, which compares very 

 closely in catkin and nutlet characters with specimens from near 

 Grand Marais, but in which the leaves average somewhat smaller 

 and are a little more narrowly cordate. 



In the Grand Marais region the large trees are scattered abun- 

 dantly through the forest on the slopes. 



In addition to this variety, the most noteworthy form is one 

 collection from near the middle of Hennepin County (Rosendahl 

 2506) in which the lateral lobes of the bracts are very short and 

 ascending or almost obsolete, and the middle lobe narrow and sharp- 

 pointed. The leaves are narrower than normal and long-acuminate. 

 Another form represented by two collections, one from Hennepin 

 County (Rosendahl 2690) and one from Dent, Otter Tail County 

 (Bergman 2858) has rhombic-ovate leaves, cuneate at the base and 

 abruptly narrowed and acuminate at the apex, and slender petioles 

 2 to 3 cm. long. In still other specimens from the west central part 

 of the state (notably Frost No. 3631) the leaves are broadly ovate 

 or nearly orbicular. 



It is possible, in fact highly probable, that some of these varia- 

 tions are the breeding out or segregation products of former crosses 

 between B. papyrifera and other species of birch of the particular 

 regions. 



Betula papyrifera x pumila var. glandulifera 

 B. Sandbergi Britton. Bull. Torn Bot. Club. 31 :166. 1904. 



A shrub or sometimes a shrub-like tree 2-10 m. high ; bark 

 dark brown, not separating into layers ; young branches rusty- 

 pubescent, in late summer or fall mostly shedding the hairs and 

 remaining merely puberulent and showing scattered resiniferous 

 dots and lenticels, 1-3 year old twigs gray-glaucous, the epidermis 

 of which splits and reveals the reddish-brown color of the perma- 



