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1913] Fernald and Wiegand, — Empetrum in North America 211 
THE GENUS EMPETRUM IN NORTH AMERICA. 
M. L. FerNaLD AND K. M. WIEGAND. 
In 1902 attention was called to the fact that we have more than a 
single Crowberry in eastern North America;! and subsequent study 
has demonstrated that, besides the cireumpolar Empetrum nigrum, 
we have in northern New England and Eastern Canada a second very 
well marked species and in Newfoundland and southern Labrador a 
third species, which is abundant upon Newfoundland and the French 
Islands but barely reaches the American Continent in the neighbor- 
hood of the Straits of Belle Isle. In checking the characters of these 
two seemingly endemic species of northeastern North America, we have 
studied closely not only the material in the Gray Herbarium and the 
herbarium of the New England Botanical Club, rich in their representa- 
tion from New England, eastern Canada, and Newfoundland; but have 
had the advantage of working with the material in the United States 
National Herbarium, with a remarkable strength in Alaskan speci- 
mens, and that of the Academy of Sciences of Philadelphia, strong in 
its representation from the Canadian Rocky Mountains. For the 
use of these two collections we are indebted to Messrs. W. N. Maxon 
and Witmer Stone respectively. 
As understood by us our Crowberries belong to three species dis- 
tinguished as follows: 
A. Branchlets or margins of expanding leaves glandular, the latter not 
tomentose; mature leaves divergent, soon reflexed. 
Berries black, with or without a bloom.......... 1. E. nigrum. 
Berries red or purple: branchlets glabrous, glandular-pulverulent or 
at most minutely viscid-pilose....la. E. nigrum, var. purpureum. 
A. Branchlets and margins of expanding leaves white-tomentose; plant not 
glandular: leaves ascending to divergent, rarely (and then very tardily) 
reflexed: fruit pink, red, or purplish-black. 
Fruit 5-9 mm. in diameter, red to purplish-black, opaque: seeds 
2-2.4 mm. long: leaves soon loosely divergent, rarely becoming 
reflexed; those of the leading shoots with blades (4-)4.5-6.5 mm. 
ROU MM UD M RENE E 2. E. atropurpureum. 
Fruit 3-5 mm. in diameter, pink or light red, becoming translucent: 
seeds 1.2-1.5 mm. long: leaves crowded, ascending, becoming 
slightly divergent; those of the leading shoots with blades 
204 mm. long..................- n AN 3. E. Eamestt. 
1. E. nigrum L. Sp. Pl. 1022 (1753); Michx. Fl. Bor. Am. ii. 255 
(1803); Pursh, Fl. i. 93 (1814); Bigelow, Fl. Bost. ed. 2, 365 (1824); 
1 Fernald, Ruopora, iv. 147-151 (1902). 
