100 DESERT VEGETATION. Chap. V. 



gryllus of the same colour feeds on it. In the case of the insect, 

 the peculiar colour is given as compensation for the deficiency of 

 the powers of motion to enable it to elude the notice of birds. The 

 continuation of the species is here the end in view. In the case of 

 the plant the same device is adopted for a sort of double end, viz. 

 perpetuation of the plant by hiding it from animals with the view 

 that ultimately its extensive appearance will sustain that race. 



As this new vegetation is better adapted for sheep and goats in 

 a dry country than grass, the Boers supplant the latter by imi- 

 tating the process by which gramnivorous antelopes have so 

 abundantly disseminated the seed of grasses. A few waggon- 

 loads of mesembryanthemum-plants, in seed, are brought to a 

 farm covered with a scanty crop of coarse grass, and placed on a 

 spot to which the sheep have access in the evenings. As they 

 eat a little every night, the seeds are dropped over the grazing 

 grounds, in tins simple way, with a regularity winch could not be 

 matched except at the cost of an immense amount of labour. 

 The place becomes in the course of a few years a sheep farm, as 

 these animals thrive on such herbage. As already mentioned, 

 some plants of this family are furnished with an additional con- 

 trivance for withstanding droughts, viz. oblong tubers, which, 

 buried deep enough beneath the soil for complete protection from 

 the scorching sun, serve as reservoirs of sap and nutriment during 

 those rainless periods which recur perpetually in even the most 

 favoured spots of Africa. I have adverted to this peculiarity as 

 often seen in the vegetation of the Desert ; and, though rather 

 out of place, it may be well, — while noticing a clever imitation of 

 one process in nature by the Cape farmers, — to suggest another 

 for their consideration. The country beyond south lat. 18° 

 abounds in three varieties of grape-bearing vines; and one of 

 these is furnished with oblong tubers every three or four inches 

 along the horizontal root. They resemble closely those of the 

 asparagus. This increase of power to withstand the effects of 

 climate might prove of value in the more arid parts of the Cape 

 colony, grapes being well known to be an excellent restorative in 

 the debility produced by heat; by engrafting, or by some of 

 those curious manipulations which we read of in books on garden- 

 ing, a variety might be secured better adapted to the country 

 than the foreign vines at present cultivated. The Americans 



