I 82 



FORMATIONS AND GUILDS 



[Part II 



of a quill to that of a finger, and producing roots and tufts of leaves 

 at their nodes. The tufts, like our sand-grasses, owe their pallor to 

 a coating of wax. 



The advantages due to this mode of growth in such habitats are 

 obvious. The creeping shoots, firmly anchored by numerous deeply 

 penetrating roots, offer a much better resistance to the wind, and incur 

 much less danger of being torn out of the loose shifting substratum 

 than do erect plants. It is therefore no wonder that many other 

 littoral plants adopt a mode of life similar to that of Spinifex, such as 



Fig. 97. Sand-dunes near New Brighton on the east coast of the South Island of New Zealand. 

 with Scirpus frondosus, Banks et Soland. From a photograph by Cockayne. 



Remirea maritima, which is almost ubiquitous in the tropics, and the 

 still commoner and more widely distributed Ipomoea Pes-caprae (I. biloba), 

 the extremely long and distantly rooted creeping shoots of which cover 

 and fix the sand with a narrow-meshed net, and also the species of 

 Canavalia that physiognomically resemble Ipomoea Pes-caprae. In the 

 north temperate zone, the sea marram (Ammophila arundinacea) fixes the 

 loose sand of the dunes by means of its extremely long and richly subdivided 

 rhizomes, and so do some other grasses, such as Elymus arenarius and 

 Agropyron junceum. .All -these plants have the important faculty of 

 again growing out of the sand, after having been covered by it. 



