ClIAI'. I] 



THE FORMATIONS 



i8i 



North Sea. Behind tlic sandy shore, here rich in lime, there rises first 

 a range of dunes poor in plants, behind which there arc dunes that arc 

 better clad and which serve as a transition to the mainland. Only the 

 flat shore and the dunes lying nearest the sea exhibit in their vegetation 

 the characteristic influence of the habitat. Difficulty in fixing themselves 

 to the loose substratum, difficulty in obtaining a supply of water, a 

 struggle against the sea-wind, the use of the wintl for the transport of 

 fruits on the smooth sandy surface, all these may at once be inferred 

 from the remarkable forms that occur. 



Fig. c|f). Nebraska. Sandy deposits with open mixed formation of plants in a river-bed. In the 

 .ickground, grassland formation (]>rairie"! corresponding to the climate, and bare rocks. Photograph 

 rom the Geological Department of Nebraska University. 



Adaptations in relation to such conditions arc combined in the 

 ".learest manner in Spinifex squarrosus, a rigid bluish grass, with large 

 ^lobular inflorescences and infructescences ', which latter appear to be 

 :omposed of long radially arranged needles, the very long bracts, 

 n-equently Spinifex alone covers the outermost dunes bounding the Indian 

 Dcean with numerous apparently independent tufts ; a closer inspection 

 hows that, in many cases, even widely separated tufts are united by 

 ■tolons more or less imbedded in sand, varying in thickness from that 



See Fig. 369 for an illustration of the quite similar infructcscence of Spinifex 

 irsutus. 



