64 ASPECTS OF TROPICAL NATUKE 



the naras the land would be all but uninhabitable. The creep- 

 ing plants of the desert serve, moreover, a double purpose ; for, 

 besides their use as food, they fix, by means of their extensive 

 ramifications, the constantly shifting sands, — thus rendering 

 similar services to those of the sand-reed {Ammophila arun- 

 dinacea) on the dunes along the sandy coasts of the North Sea. 



The Mesembryanthemums are another family of plants ad- 

 mirably adapted to the desert, as their seed-vessels remain 

 firmly shut while the soil is hot and dry, and thus preserve the 

 vegetative power intact during the highest heat of the torrid 

 sun ; but when rain falls the seed-vessel opens and sheds its 

 contents, just when there is the greatest likelihood of their 

 vegetating. This is the more wonderful, as in other plants 

 heat and drought cause the seed-vessels to burst and shed their 

 charge. 



One of this family is edible (if. edule) ; another possesses a 

 tuberous root, which may be eaten raw ; and all are furnished 

 with thick, fleshy leaves, with pores capable of imbibing and 

 retaining moisture from a very dry atmosphere and soil ; so 

 that if a leaf is broken during the greatest drought it shows 

 abundant circulating sap. The oblong tubers, with which some 

 of the mesembryanthemums are furnished, serve them as an 

 additional means for withstanding the want of rain ; for, being 

 buried deep enough beneath the soil for complete protection! 

 from the sun, they serve as reservoirs of sap during those rain- j 

 less periods which recur very frequently in even the most! 

 favoured spots of these parts of Africa. 



Many useful plants have been conveyed from one country toj 

 another ; but I doubt whether any attempts have as yet been! 

 made to acclimatise the tuberous cucurbitacese and the mesem-j 

 bryanthemums of Southern Africa in the northern deserts of! 

 that continent, or on the arid coast of Peru, where perhaps! 

 some of them might thrive and prove of great use. Thei 

 propagation of all that is beautiful or useful in nature to every! 

 other part of the world adapted to its growth, will be a workj 

 for future generations. i 



The peculiar and comparatively abundant vegetation of thej 

 arid plains of South Africa explains how these wastes are peopled 

 by herds of herbivorous animals, which in their turn are preyed^ 

 upon by the lion, the panther, or the python. Hundreds oil 



