VEGETATION OF BLAKENEY POINT. 31 



numerous scattered plants of Obione portulacoides, which, 

 however, is prostrate in habit, seldom attaining more than two 

 or three inches in height or a foot in diameter. To these 

 species must be added Armeria maritima and stunted 

 plants of Glyceria maritima and Plant ago Coronopus, the 

 latter usually with almost glabrous and 'but slightly toothed 

 leaves. 12 



(4.) The Crest. (Fig. 13). 



The fourth zone forms the larger part of the bank, and is a 

 grassy sward of numerous species in which the dominant 

 plants are Armeria maritima, Silene maritima and Agrostis 

 maritima. 



Common in this zone also are Sedum acre, Arenaria 

 serpyllifolia and Plantago Coronopus ; the first two are 

 usually associated together, and the last frequently with 

 Cladonia rangiferina, especially towards the base of the 

 banks. Trifolium arvense, Trifolium striatum, Cerastium 

 tetrandrum, Sagina maritima, and Lepturus filiformis, have 

 a distribution which coincides roughly with the tracks, formed 

 by the coastguards and others, which usually pass along the 

 main axes of the banks. This habitat is probably to be inter- 

 preted as due to the low growth and barer character of 

 these places, rather than to direct human agency in their 

 distribution. Such a view seems to be borne out by the fact 

 that some of these species are most abundant on banks where 

 the amount of traffic is not greatest. In the case of Lepturus 

 filiformis, there is a decrease in amount as we pass from 

 the older to the younger laterals, till on bank No. 8, which is 

 probably visited more than any other on account of the Watch- 

 house, the species is entirely absent. The mode of occurrence 

 of several of these plants in other localities and formations is 

 also in accordance with the view here expressed. 



Owing to the exceptional character of bank No. 5, mentioned 

 above, the whole of its flat top is occupied by the Binervosa 

 association, and the crest plants themselves are altogether 



12 On Bank No. 8, and there only, we find in this association in one place 

 plants of Spergularia salina. 



