L66 OUTLINE OF PLANT GEOGRAPHY 



At higher altitudes in the mountains there is a marked increase 

 in rainfall, and in the valleys and more sheltered situations, 

 a true rain-forest is developed. 



Further south the coast is very arid, and finally true desert 

 conditions prevail. 



The most remarkable plant of this district is the extraordinary 

 Tumboa (Welwitschia) which has no near relatives elsewhere. 

 It belongs to the small order Gnetales, which in some respects 

 is intermediate between the true gymnosperms (conifers and 

 cycads), and the higher flowering plants. Welwitschia has a short 

 woody trunk which sends a long tap-root deep into the ground, 

 and bears two great persistent, strap-shaped leaves, generally 

 split into ribbons, which are all the plant ever develops. This 

 desert coast region is continuous with the great Kalahari desert 

 of South Africa. 



The Great Kamerun 



The high volcanic peaks of equatorial Africa show, as might 

 be expected, great changes in vegetation as one ascends. The 

 great peak of Kamerun (13,370 ft.) has been carefully studied, 

 and will serve as an example. 1 



At the base of the mountain, where the land has not been 

 cleared, is a lofty rain-forest of the most pronounced type. Where 

 the cultivated land has been abandoned, a second growth forest 

 of a very different character soon occupies the clearings. This 

 second growth forest contains many species which are unable 

 to grow in the dense shade of the primitive rain-forest. Areas 

 of meadowland and savanna also develop in the cleared spots, 

 and in more open places are many attractive herbaceous plants, 

 some having handsome Mowers, like Crinum, with big lily- 

 like blossoms, or balsams (Impatiens) with attractive flowers 

 of various colors. Ferns and some of the numerous gingers, 

 are noticeable for their fine foliage, and some of the latter, also, 

 have showy flowers. 



A very characteristic grass of this region is the elephant-grass 

 {Pennisetum purpureum) which is ordinarily some ten feet in 

 height, but may exceed this. This very valuable forage grass 

 often covers extensive areas, and only permits a scattered growth 



1 Engler, loc. cit., p. 758. 



