The Growth-Forms of Natal Plants. 
607 
nised. We are a long way from the ultimate goal of a proper ecological 
interpretation of the various growth-forms. At present any investigation of 
the subject must follow certain lines. 
The first essential is as thorough a knowledge as possible of the complete 
life-history (autecology) of each species. How very far we are from this ideal 
is being realised more and more clearly by all plant ecologists. In a recent 
paper (16) Prof. F. W. Oliver remarks : " Of the 120 species of flowering 
plants that form the known flora of Blakeney Point, it is doubtful whether 
we can truly assert that we are really familiar with the full life- histories 
of more than two or three." If this is true of a country like England, 
where there are so many workers, the difficulties confronting a single 
worker in a country like Natal can be better appreciated. 
Of the habits of Natal plants and their full life histories, as studied in 
the field, really very little is known. Many of them are only known as 
herbarium specimens, and many more — in fact, the majority — have been 
named and described in the only available systematic work. The Flora 
Cajpensis, by botanists who have never seen them growing. It is not 
surprising, therefore, to find that growth-forms have received either very 
scant attention or none at all, or what is worse, incorrect information has 
been given. Apart from this, however, to a plant ecologist working in a new 
country, it is very useful to have some sort of a "Flora," or at least a list of 
species, to serve as a guide. Medley Wood's List of Natal Plants (26) is, 
therefore, of great assistance. Nor is it to be supposed that the Flora 
Caioensis is in any way inferior to other similar works, in respect to the 
descriptions of growth-forms. As already remarked, " G-rowth-forms are too 
often very imperfectly described, even in the standard British floras " (22). 
Sim's Forests and Forest Flora of the Cape of Good Hope (21) contains 
much information regarding the growth-forms of the trees and shrubs. 
The choice of a system of classification for growth-forms is a matter of 
the greatest difficulty. The guiding principle must be natural — i.e. the 
system must in itself show the dependence of the growth-forms on external 
factors— but the present state of our knowledge is such that any attempt at 
such a system must remain incomplete and unsatisfactory. 
A short historical summary of the various systems that have been 
proposed is given in Warming's Ecology of Plants, ch. ii. The earliest 
is that of Humboldt (1805) — a purely physiognomic system, not founded on 
ecology (7, 8, 9). G-risebach (1872) put forward another physiognomic 
system, which he claimed, without good grounds, showed the influence of 
environment, particularly climate. 
The systems of Drude (4), Krause (10), Pound and Clements (19), 
Raunkiaer (20), and Warming followed, all based on various ecological 
principles. It is unnecessary in this paper to repeat the summary of each 
given by Warming. The systems of Drude, Pound and Clements and 
