188 Fernald — Relationships of some American 



ward, and locally south to Morris Co., New Jeesey, Champaign 

 Co., Ohio, Lake Co., Indiana and McHenrj Co., Illinois, in 

 Greenland, northern Europe and Siberia. The leaves vary 

 much in outline and in the degree of permanence of the pubes- 

 cence ; and the samaras in the breadth of the wings and achenes. 

 Narrowly obovate and orbicular leaves are often found upon 

 the same shrub, so that species or varieties based upon these 

 cliaracters (as J^. Grayi, Kegel, Bull. Soc. Imp. Nat. Mosc. 

 xxxviii, 406, t. 6, figs. 9-13) have little value. 



Betula pximila^ var. glanduUfera. 



In the Great Lake region, however, and from there north- 

 ward and westward, where Betula pitmila meets B. glandu- 

 losa, it presents a perplexing form. In its long pubescence 

 (when well developed) the shrub seems to be B. pumila^ but 

 mixed with the pubescence and sometimes upon the leaves are 

 the characteristic glandular atoms of B. glandulosa. Ordi- 

 narily, though, the shrub is readily distinguished from the latter 

 species by the longer pubescence of the young shoots. This 

 intermediate and transitional form, Betula puinila^ var. glan- 

 duUfera^ Kegel in DC. 1. c, occurs from western Ontario and 

 Michigan to Minnesota, Saskatchewan and British Colum- 

 bia, south to Idaho and Oregon. 



Betula glandulosa. 



Betula glandidosa'^ presents two variations which in their 

 extreme developments appear very distinct, but which again 

 so mingle their characters as to be quite inseparable. Typical 

 B. glandulosa is an upright shrub sometimes several feet high, 

 but in exposed situations it becomes dwarfed and widespread- 

 ing. In the typical form of the species the leaves are obovate, 

 but occasionally on these shrubs orbicular or reniform leaves 

 are found. This shrub with obovate leaves is most common in the 

 interior of North America, from the Yukon and Mackenzie 

 Rivers to Hudson Straits, south in the mountains to northern 

 California, Utah, Colorado, and South Dakota ; across the 

 plains to Manitoba and Lake Superior ; and through Labra- 

 dor and locally to the higher mountains of northern New 

 England. It is also in Greenland, Kamtschatka and the 

 Altai Mountains. 



On the eastern mountains (Albert, Katahdin and Washing- 

 ton), in Labrador, and in the Altai the shrub passes imper- 

 ceptibly to a form with orbicular or reniform leaves, var. 

 rotiondifolia^ Eegelf {Betula rotundi folia, Spach;}:) ; but on 



* Michx., Fl. Bor.-Am. ii, 180 (1803). f Kegel in DC, 1. c. 172 (1864). 



X Spach, 1. c. 194 (1841). 



