1867.] DRUMMOND — DISTRIBUTION OF PLANTS. 165 



induce the withholding of any conclusion. Besides, it seems diffi- 

 cult to escape the conviction that very often local circumstances — 

 to some of which reference will hereafter be made — will, more 

 than the general climate or the presence of any particular ingre- 

 dients in the soil, account for the occurrence of plants in specific 

 localities. 



Other features of interest may be also cited. Those who have 

 visited the Thousand Islands in the River St. Lawrence must 

 have been struck with the vast abundance of Rhus typhina Linn, 

 and Pteris aquilina Linn. Neither of these plants is, however, 

 limited to Laurentian soils, and it is very probable that the pro- 

 fusion here of at least the former is in part due to the rugged, 

 rocky nature of almost all of the islands. It may be also men- 

 tioned that the capacity of land for cultivation is often in Canada 

 judged of by the timber trees growing naturally upon it. Eastern 

 farmers look upon the red pine, Plnus resinosa Aiton, as character- 

 izing a poor soil, whilst there are many in the Erie district, where 

 the red pine is unknown, who regard the chestnut, Castanea vesca 

 Linn, as evidencing some sterility. 



Another circumstance affecting distribution is not to be over- 

 looked. The Laurentian rocks, which are very largely developed 

 in Canada, are remarkable for their rugged, corrugated character — 

 in some places forming ranges of high hills, in others, individual 

 elevations of considerable height, and everywhere, to a greater or 

 less extent, displaying the same characteristic rugged surface. 

 The whole breadth of the strata is, besides, dotted with basins of 

 varying sizes and forms, which have been worn out of the softer 

 material of the rock, and are now filled with sheets of water. The 

 surface of the Laurentian rocks is, to a very considerable extent, 

 bare and only tenanted by numerous saxicolousParmelias, Lecideas. 

 and other lichens, with mosses and some ferns, and a few often 

 stunted phanerogams maintaining an existence in the little soil 

 collected in the frequent cracks and fissures. The very numerous 

 little hollows and depressions in the surface — probably in most 

 instances grooved out by the action of ice — are covered by a layer 

 of soil generally scanty, but which is often very rich and supports 

 a prolific vegetation. On the other hand, the Silurian and 

 Devonian formations have either a level or somewhat undulating 

 surface, and are everywhere covered by clays, sands, gravels and 

 loams, which attain very often a great thickness, especially in the 

 Upper Canada peninsula, where numerous illustrations are afforded 



