152 Canadian Record of Science. 



the prairies probably dates its origin within a compara- 

 tively recent period. Certainly these prairie fires now 

 prevent the encroachments of the forest upon the plain? 

 as otherwise these forests would in the natural order of 

 things extend themselves westward and southward if 

 allowed to do so. The same is true of the bluffs or 

 stretches of timber found growing in frequent places south 

 of the true forests, though even there the trees are of 

 relatively moderate size proving that these bluffs are of 

 comparatively recent or of very slow growth. There can 

 be no question that as prairie fires cease with the progress 

 of cultivation of the land and with the enforcement of pre- 

 ventive laws, the tendency of these stretches of timber and 

 of the true forests will be to extend themselves further over 

 the prairie. In the meantime, the effect of the absence of 

 timber is to create a drier climate by diminishing the rain- 

 fall, and on account of the general flatness of the prairie by 

 exposing every object upon it to constant and unbroken, 

 drying winds. That there is, therefore, a general tendency 

 of trees to skirt the river banks can be readily understood, 

 as there they obtain that moister atmosphere which is 

 absent on the open prairie. Even in the valleys of such 

 great streams as the Assiniboine and the Qu'Appelle, trees 

 are generally found on the southwestern or western sides, 

 the eastern being frequently bare, and this can only be 

 accounted for by the greater protection from drying winds 

 the western and southern banks have, and therefore the 

 greater moisture in the soil there. 



Again, only in the river valleys, on and near the lake 

 margins and on the hills or rising grounds are the forest 

 trees of the North-west completely represented, and it is 

 suggestive whether the trees there are not the relics of a 

 larger forest flora which more or less covered the whole 

 country. At present the cosmopolitan poplars are the chief 

 occupants of the plains, their very hardiness, however, con- 

 stituting them fitting pioneers of new forests some day to 

 appear. 



I cannot help thinking that as the prairies become thickly 

 settled and protective laws are properly enforced, prairie 



