The Growth- Forms of Natal Plants. 
621 
in the bush for example, one plant affects another and the non-living 
environment is highly modified. The result is that the same species varies 
very greatly, according to whether it grows gregariously in the bush or 
isolated outside the bush. This presupposes, of course, that the species is 
sufficiently accommodating to do so, but the examples of trees and shrubs 
which are of this nature are very numerous in Natal. 
However, this difficulty would arise, no matter what basis for subdivision 
were selected. Raunkiaer's system, as a whole, endeavours to arrange 
growth-forms in a definite series, showing increased protection to the 
growing apices during the adverse season. The Nanophanerophytes are 
supposed to show greater protection than the Microphanerophytes. In the 
main this is the case, yet we find Microphanerophytes — e.g. Acacia spjj. and 
numerous other trees — fully exposed to the dry, hot winds, and extremely 
adverse environment of the Thorn Veld ; while Nanophanerophytes — e.g. 
species of Justicia and other Acanthaceae, Fiper capense, etc. — occupy the 
sheltered, moist environment of the Bush. Here, then, are members of a 
class, which, according to Eaunkiaer's scheme, ought to show greater 
protection, occupying a habitat where such greater protection is not 
required. 
As a matter of fact, except in height, such species do not show greater 
protection. Most of them are distinctly mesophytic. The difficulty arises 
again from the choice of a single factor as a basis for classification. By 
choosing height as the basis for subdividing the Phanerophytes, Eaunkiaer 
certainly gained by making his system very easy to apply. In temperate 
regions, where the forests in winter do not afford the same protection to the 
undergrowth and where frost and snow have to be taken into consideration, 
the height of a species is a more certain guide than in a subtropical country 
like Natal, and shows a truer ecological relationship. But in all countries, 
and especially in countries with evergreen forest, the height of species must 
remain a somewhat artificial basis for classification. 
The dominant trees of the forest are certainly taller than the trees of 
the Thorn Veld, the latter thereby showing reaction to more adverse con- 
ditions, but the undergrowth of the forest enjoys a more favourable environ- 
ment than the trees that afford it a protection ; yet the undergrowth cannot 
from the nature of things obviously grow taller. It is not necessary to 
labour the point. Enough has been said to show that Eaunkiaer's scheme 
does not in its details show strictly the reaction to the adverse season. At 
the same time, it is difficult to improve it without detracting from its chief 
merit — the ease with which it can be applied. There does not seem to be 
any other single character that would suit l)etter than height as a basis for 
the subdivision of the Phanerophytes. 
