136 PLANT-LIFE ON LAND [CH. 



sand are features of still greater moment as bearing 

 upon its value as a sand-binder. 



Hidden in the sand are the long horizontally 

 running rhizomes of the Marram Grass that are 

 densely matted together, and are thus so marked a 

 factor in its success (Fig. 23). On them the leaves 

 are borne alternately at long intervals, and develope 

 only their lower sheathing part while the lamina 

 remains small. These rhizomes are found to be firm 

 and resistant like strong cord, and their mechanical 

 strength is again an important point. They may be 

 traced for long distances, and are found throughout 

 the structure of the Dunes, even to their base. At 

 each node where a leaf is inserted a number of roots 

 may arise, radiating outwards into the sand, while 

 in an axillary position a bud originates, the mode 

 of development of which may vary according to 

 circumstances (Fig. 24). It may grow horizontally 

 with long internodes, and become a new runner, 

 having its terminal bud sharpened and indurated 

 like the point of an awl : or it may turn upwards 

 and form a leafy shoot, which on emerging at the 

 surface of the sand will, by shortening its internodes 

 and developing its axillary buds, form one of those 

 dense leafy tufts so characteristic of the species. 

 It is the adaptability of this grass to its circumstances 

 in respect of direction of growth of its shoots, and 

 the degree of elongation of its internodes, combined 



