52 



THE PLANT SOCIETIES OF 



ter of fig. JO is seen in closer view in fig. i ; the absence of vegeta- 

 tion, save that which has slid down from above, is very striking. 



If for any reason the lake activities at the base of the cliff are 

 stopped, an opportunity is offered for the development of vegetation. 

 At Glencoe the cliff erosion has been checked to some extent by arti- 

 ficial means, and one can see various phases of cliff life within a small 



Fig. 30. — Sea cliff along the eroding shore at Glencoe, exposing the morainic clay. Vege- 

 tation almost entirely absent. Proiecting turf mats at the top show the tenacity with which 

 the vegetation holds its ground in the lace of the erosive forces. 



area. When the erosion at the base of the bluff ceases, conditions be- 

 come much more stable, though l^dslide action may still occur. In 

 time the slope gradient becomes so low that the cliff soil is essentially 

 stable ; when this time arises vegetation develops with great rapidity 

 in spite of the xerophytic conditions, which are still as pronounced as 

 before. It is very obvious, therefore, that it is the instability of the 

 eroding cliff and not its xerophytic character which accounts for the 

 absence of plant life. 



The first vegetation is commonly made up of xerophytic herbs, 

 both annual and perennial. Among these are the sweet clover (^Melt- 

 lotus alba), various annual weeds, various species of Aster, especially 



