Ecological Notes. 
AFRICAN PARK-LANDS. 
[Plate II.] 
T HE most fundamental classification of the different types of 
vegetation covering the earth’s surface is that into Forest, 
grass-covered Steppe, and Desert. In his great work on Plant- 
geography 1 Schimper ably summarises the climatic conditions which 
govern the occurrence of one or other of these great “ formations ” 
over any tract of country. He comes to the conclusion that the 
main conditions under which Forest occurs are a comparatively 
warm vegetation period, a constant supply of water in the lower 
strata of soil reached by the roots of the trees, and a comparatively 
damp and still atmosphere. Grass-covered Steppes, on the other 
hand, demand for their existence frequent, if only slight, rainfall so 
that the surface of the earth is kept moist during the period of 
active growth, and a moderate equable temperature. In a general 
way, and apart from special conditions, the existence of one or other 
of these types of climate will determine the victory of one or other 
of these types of vegetation. 
An intermediate type of vegetation, the Savannah or Park-Land 
in which grass-covered plains are dotted here and there with single 
trees or clumps of trees and shrubs, is however, characteristic of 
enormous stretches of country in the tropics, particularly in South 
America and in Central Africa, and this, according to Schimper and 
others, owes its existence to the prevalence of an intermediate type 
of climate, so that the balance is held, as it were, between the grass- 
formation and the forest-formation, and neither can gain tjie 
predominance. Schimper supports this theory by statistical data of 
rainfall, etc., and concludes that when there is a mean annual rainfall 
of more than 72 inches, typical forest occurs, while with a/rainfall of 
36 to 60 inches, we have a struggle between the grass-formation and 
the xerophilious forest. 
Mr. J. E. S. Moore, however, in his recent fascinating volume 3 
containing the scientific results of the two Tanganyika Expeditions, 
has thrown quite a new light on one aspect of this general question, 
and offers a convincing solution of the problem of how the Park- 
Lands, observed by him extending over great tracts of country 
between the Zambesi and the Albert Nyanza, have originated. 
Stated in general terms Mr. Moore's view is that park- 
1 A. F. W. Schimper: Pflanzeiigeographie, 1S98, pp. 176-190. 
2 The Tanganyika Problem, by J. K. S. Moore, London. Hurst 
and Blackett, 1903. 
