150 Canadian Record of Science. 



land by the successive annual growth and decay of these 

 grasses, circumstances existed which rendered the growth 

 of forest trees impossible. Great tracts of country are still 

 in this condition. There are also many areas of great ex- 

 tent, as on the Pembina branch of the Canadian Pacific Bail- 

 way, around Gladstone and Westbourne on the Manitoba & 

 Northwestern Eailway, and between Baie St. Paul and Lake 

 Manitoba, where, during the wet seasons — and these seem 

 periodically to follow each other for two and three years in 

 succession — very extensive tracts of magnificent prairie 

 land, which in other seasons are dry and capable of cultiva- 

 tion, are practically under water for most of the summer 

 months. Thus trees, which in dry seasons might spring up 

 in such stretches of country, would during the successive 

 wet seasons be gradually killed. Wherever such conditions 

 have prevailed, whether in far distant or present times, 

 forests, for the time, could not be expected to appear. 



The question however arises whether, once the condition 

 of dry land was attained, did trees spread over the prairies 

 as they have elsewhere, and whether subsequent causes may 

 not have prevailed in removing them. That certain trees 

 will freely grow on the prairies is proved by the frequent 

 bluffs of timber, especially to the north of the Assiniboine 

 and Qu'Appelle. These bluffs often occur in stretches of 

 miles in extent and often again are found isolated. North 

 of the Qu'Appelle they are so frequent as to give the coun- 

 try a park-like appearance and to render that country very 

 attractive for settlement. Beyond this point northward 

 they continue to occur until they finally merge into the true 

 forest region which in this section extends from Lake Win- 

 nipeg westward to the sources of the Athabasca Biver, and 

 from between these localities northward to the extreme 

 limits of forest growth — including within this are a great 

 stretches of what should correctly be termed prairie coun- 

 try. On the prairies proper the prevailing trees are the 

 poplars, and only in the deep river valleys or skirting the 

 margins of the lakes and the smaller streams and on the 

 hills are the other trees of the prairies found in numbers. 



It is quite true that the total number of species of trees 



