The Growth-Forms of Natal Plants, 
633 
The normal spectrum is given by Raunkiaer as approximately that of the 
whole world's flora. It was obtained by computation and checked in various 
ways. The other spectra must be judged by the amount of variation from 
the normal in each of the separate life-forms, and not by the highest 
percentage of each. E-aunkiaer's statistics refer only to the Northern 
Hemisphere. He uses them to establish certain regional climatic zones, for 
a full explanation of which Smith's paper may be consulted (22). It is 
unfortunate that no statistics are available for the Southern Hemisphere. 
No climate zone can as yet be established here, but from the above table 
certain general conclusions can be drawn which apply to Natal as to other 
countries. 
If the optimum point of the Biological spectrum is toward the left — i.e. 
in the groups M.M. and M. — it means that we have a favourable type of 
climate for tree growth— i.e. a Phanerophytic climate. A shifting of the 
optimum point to the right means increasing drought or other adverse 
conditions (frosts, etc.), particularly at one season of the year. We thus 
pass first to a Chamaephytic and then to a Hemicryptophytic type of climate. 
Still more severe conditions, dry summers, or general drought leads to a 
desert type or Therophytic type, the Therophytes being very abundant. The 
application of this Therophyte test enabled Ove Paulsen (18) to class the 
Transcaspian lowlands as desert rather than steppe. The Therophytes also 
increase in more highly cultivated areas — e.g. Denmark, Stuttgart. 
GENERAL SUMMARY AND CONCLUSIONS. 
The analysis of the flora shows that in Natal we have every type of life- 
form represented, indicating a rich and varied flora and corresponding 
variation in the environmental conditions. The same thing is shown by the 
large total number of species, 3074 (which does not include quite all the 
known species), and also by the variability seen in the growth -forms of 
the same species, especially among the Phanerophytes. The Megaphanero- 
phytes are few in number and the Mesophanerophytes also fall below the 
normal, the class M. M. being 3 per cent, in Natal as compared with 6 per 
cent, in the normal spectrum. Tall trees are therefore not characteristic of 
Natal. Microphanerophytes (trees and shrubs below 8 metres) reach 14 per 
cent, as compared with 17 per cent., and Nanophanerophytes (shrubs under 
2 metres) are 14 per cent, as compared with 20 per cent, in the normal 
spectrum. 
Taking the Phanerophytes as a whole we see that they fall considerably 
below the normal, 31 per cent, instead of 43 per cent. 
Seychelles, with a typical Phanerophytic climate, has 57 per cent. Phanero- 
phytes, Danish West Indies 58 per cent. On the other hand. Natal has many 
