1867.] DRTTMMOND — DISTRIBUTION OF PLANTS. 163 



strata. It would be interesting, however, to compare the range, 

 in relation to soils, of those plants which are common to 

 Europe and America. 



We can conclude from the known distribution in Canada of 

 rocks of the earlier geological formations, and from the direction 

 of the ice-grooves upon them, that soils composed chiefly of Lau- 

 rentian, or, in some instances, Huronian debris, were spread both 

 over these formations and for at least some distance over the Silu- 

 rian and Devonian rocks during the epoch of the drift, whilst the 

 strata farther south were carpeted with more calcareous soils. 

 The distribution of these soils was, no doubt, at subsequent periods, 

 somewhat disturbed. Now, the Laurentian strata are composed of 

 such different materials in different localities — some of which lie 

 at but comparatively short distances apart — that knowing the 

 composition of the soil at any given locality, it would be often 

 incorrect to assign a similar composition to soils in the vicinity 

 which we know must have been derived from rocks of the same 

 system. The quartzites have afforded silica in abundance to the 

 soil ; the limestones, phosphate and carbonate of lime, and other 

 minerals in variable quantities ; the dolomites, carbonates of lime 

 and magnesia; the serpentines, silica and magnesia; and the 

 orthoclase and labradorite, silica, alumina, soda and potash. All 

 of these mineral species, with others, are common in the Lauren- 

 tian rocks. The Huronian formation also abounds in quartzites 

 and dolomites. Within the limits, then, of a single township there 

 might be met with soils in one case highly calcareous, in another 

 with noticeable quantities of alkalies and but a trace of lime. The 

 very variable proportions in which the same chemical ingredients 

 will frequently occur in soils, at localities not far distant from each 

 other, has been well shown by Dr. T. Sterry Hunt.* It is a 

 noticeable circumstance that lime, potash and soda, appeared in 

 all the soils analyzed by him. These facts are mentioned to show 

 that if the composition of soils has such an influence as to affect 

 the presence of plants upon them, conditions must occur in some 

 parts of but limited areas favourable to the existence of many 

 plants which do not in others. Moreover, when we consider the 

 varied compositions of our early formations, it is easy to conceive 

 that over the immense extent of country in which they are deve- 

 loped, whilst many situations afford the requisite conditions for 



* Geology of Canada, \^(\^, p. 640. 



