of the White Mountains, 95 



of such plants except on certain hills. At Murray Bay, and on 

 the shores of Lake Superior, the plant above named occurs only 

 on the Laurentian gneiss. In Nova Scotia, its relative, Corema 

 Conradi, is confined to the granite barrens of the south coast. 

 Many such plants skirt the whole Laurentian range from Labra- 

 dor to Lake Superior, but refuse to extend themselves over the 

 calcareous plains of Canada. But in the White Hills the soil of 

 the river alluvium is the same micaceous sand that fills the cre- 

 vices of the rocks in the mountains, and hence there is no ob- 

 struction, in so far as soil is concerned, to the diff'usion of plants 

 upward and downward in the hills. In like manner there is every 

 possible condition as to moisture and dryness, sunshine and shade, 

 in both localities. These circumstances are of all others the most 

 favourable to such variation as these plants are capable of under- 

 going. The case is the same with that which Hugh Miller so 

 strongly puts in relation to the species of algae that occur at dif- 

 ferent distances below high water mark on the coast of Scotland, 

 each species there attaining a certain limit, and then instead of 

 changing to suit the new conditions, giving place to another. So 

 it is on Mount Washington ; and this whether we regard the 

 lowland plants that climb to a certain height and there stop ; the 

 plants that are common to the base and summit, or the plants 

 that are confined to the latter. 



I have already referred to the evident struggle of the spruces 

 and firs, and the plants associated with them, to ascend the moun- 

 tain ; and the same remark applies to all the plants that one after 

 another cease to appear at various heights from the lower valleys. 

 One by one they become stunted and depauperated, and then 

 cease, without any semblance of an attempt to vary into new and 

 hardier forms. And this must have been proceeding, be it ob- 

 served, from all those thousands or myriads of years that have 

 elapsed since the elevation of the mountains out of the glacial seas. 

 It is to be observed also that the new plants that occur in ascend- 

 ing, often belong to different genera and families from those left 

 behind, not to closely allied species ; and in the few cases in which 

 this last kind of change occurs, there is no graduation into interme- 

 diate forms. For instance Solidago thyrsoidea and >S^. vi>ya-aurea 

 occur around the base of the mountain, and for some distance up 

 its sides. At the height of four to five thousand feet, the latter only 

 remains, and this in a dwarfish condition. This corresponds to 

 its distribution elsewhere, for according to Richardson it occurs in 



