124 



contact with the soil is sufficient protection, save in the most extreme cases. 

 These plants, therefore, while not strongly developed in the upper beach, 

 are rarely wanting on active dunes. The willows commonly found are 

 S. Ynviatilis, gloucophyUa and adenophylla. The dogwoods are C. stol- 

 inufera and Baile.iji. The i)oplar is the cottonwood, P. deltoides. To the 

 botanist, the adaptation of these plants for such a position are self-evident, 

 but indi\idual cases present continual variations. Nothing could more 

 clearlj illustrate the extreme ])Iasticity of these shrubby species than their 

 quick and sure response to these constantly varying factors. 



'41^. 



These grasses lead in the attack upon the dunes. These 

 plants all arise from a single root stock. 



In the case of the grasses, which are chiefly Andropogon. scoparius, 

 Ainniophila arenuria, Cakiiiiovilfa loni/i folia, and Eleymus canadensis, there 

 is a quick setting of roots from the nodes when there is but a partial sub- 

 mei'gence, while the long, hori^.ontal branching root stock is constantly 

 sending up new stools during the continuance of favorable conditions. The 

 first plants to obtain a foothold upon these shifting sands are usually the 

 grasses. From a single stool through the agency of the root stock there is 

 a rapid spread which covers a very considerable area. In various places 

 upon the most active portion of the dunes some one or more of these grasses 

 obtain a foothold and sti'uggle fiercely to maintain the place they have 

 seized. So far as my personal observations go. the invasion of the dune is 



