GEOGKAnilC LIMITS OF TREES AND SHRUBS. 603 



FOREST TREES AND SHRUBS. 



Many species of trees wliicli together constitute a large part of the 

 eastern forests extend to the Red River liasin, reaching there the western 

 or northwestern boundary of their range. Among tliese are the hasswood, 

 sugar maple, river maple, and red maple, the three species of white, red, 

 and black ash, the red or slippery elm, and the rock or cork elm, the but- 

 ternut, the white, bur, and black oaks, Ironwood [Ostnja vir(/ii>ica Willd.), 

 the American hornbeam (^Carjnnus caroliniana Walt.), the yellow birch, the 

 large-toothed poplar, white and red pine, arbor-vitn?, and the red cedar 

 or savin. A few species of far northern range find in this district their 

 southern or southwestern limit, namely, our two species of mountain ash, 

 the balsam poplar, Banksian or jack pine, the black and the white spruce, 

 balsam fir, and tamarack. 



Some of the eastern shrubs which make the undergrowth of our forests 

 also attain here their western limits; but a larger proportion of these than 

 of the forest trees continues west along the stream courses to the Saskatch- 

 ewan region, the upper Missouri, and the Black Hills. Among the shrubs 

 that reach to the borders of the Red River basin, but not farther westward, 

 or at least southwestward, are the black alder or winterberry, the moun- 

 tain holly, the staghorn sumach, the hardback, the huckleberry, the dwarf 

 bluebeny and the tall or swamp blueberry, leatherwood, and sweet fem. 

 Shrubs and woody clindiers that have their northern or northwestern 

 boundary in this basin include the prickly ash, staff tree or shrul)by bitter- 

 sweet, frost gTape, Virginian creeper, and the four species of round-leaved, 

 silky, panicled, and alternate-leaved cornel. On the other hand, shrubs of 

 the north which reach their southern or southwestern limits in the Red 

 River basin inchide the mountain maple, the few-flowered viburnum and 

 withe-rod, several species of honeysuckle, the Canada blueberry, the cow- 

 berrj", Andromeda polifoUa/L., Kalmia qlauca Ait, Labrador tea, the Canadian 

 shepherdia, sweet gale, the dwarf birch, green or mountain alder, beaked 

 hazel-nut, *S'rt//.r Indsamifcra Barratt, and S. myrtillokles L., var. pedicellaris 

 Anders., black crowberry, creeping savin, and the Aanericau yew or ground 

 liemlock. 



