090 



PROCEEDINGS OF THE 



boiling. " Whenever a halt is made upon the marches across the 

 wilderness, the bearers, as soon as they are liberated from their 

 burdens, set very vigorously to work and grub up all sorts of roots 

 from the nearest thickets." "I can myself," continues the same 

 traveller, " vouch for a fact, which might fairly be deemed in- 

 credible, that thirty Bongo, who accompanied me on my return 

 to Sably at a time when I had scarcely enough to keep me from 

 starvation, subsisted for six consecutive days entirely on these 

 roots, and, although we were hurrying on forced marches, lost 

 neither their strength nor their spirits. Their constitutions were 

 radically sound, and they seemed formed to defy the treatment of 

 their inhospitable home." " Incalculable in its effect," says the same 

 observer, "must be the influence of the annual steppe-burning on 

 the vegetation of Central Africa, this being favoured bv the 

 dryness of the seasons, the ground being covered with a blackened 

 ash, from which the alkalies are washed into the soil by the first 

 rain, while trees have not the same chance of attaining great size 

 that they have in temperate regions where such fires do not occur." 

 In the steppes of Europe and Asia, where the soil generally 

 consists of a coating of vegetable mould over clay, no plants with 

 deep roots thrive ; hence steppes are destitute of trees, and even 

 bushes are rare, except in ravines. The grass is thin, but 

 nourishing ; while Hyacinths and other bulbs, together with 

 Asparagus and Liquorice, grow abundantly. Bulbous Amarylli- 

 daceae abound in the meadows of Eastern Siberia, and the 

 vegetation bears a great analogy to that of North-west America — 

 several genera and species being common to both. On the North 

 American prairies, among other Compositae, occur Dahlias (Helian- 

 thus corco2)sis), &c. Again, the Llanos of Venezuela and Guiana 

 are covered with tall grass, mixed with Lilies and other bulbous 

 llowers. In these regions fires are of frequent occurrence. The 

 same is also the case in Chili, the home of the Potato. Here this 

 plant has a tendency to become woody and bristly. It is a native 

 of the sea strand, and is never found naturallv more than 400 feet 

 above it. In the wiid state the tubers of the Potato are small, 

 and, like those African tubers already referred to, bitter. Indeed, 

 the most of the order Solanacese, to which it belongs, possess bitter, 

 poisonous principles. The fibrous character of the rootlets of the 

 Potato, as well as the fact that it prospers best in dry, sandy soils, 

 together with those crop failures in very wet seasons, unmistakably 



