1224 
MESSRS. J. B. LAWES, J. H. GILBERT, AND M. T. MASTERS, 
and Aster salignus, A. parviflorus, Euphorbia virgata, and Prunus Padus, derived 
from the garden. 
It may, therefore, be inferred that the district in which these experiments were 
made would in process of time, if no obstacle were afforded, become covered with 
meadows and woods—meadows in the low-ground and woods in elevated places. 
Again, the experiments show that the survival of certain plants has not been mate¬ 
rially influenced by the nature of the soil. Thus, Triticum repens was ultimately 
spread over all the plots, whether of sand or of loam or of lime; whether drained or 
undrained. So also with Poa pratensis and Potentilla reptans. 
As to the action of shade, it was found that low-growing plants, especially if 
annuals, disappeared rapidly ; while taller-growing ones, such as the Triticum, Prunus 
Padus, &c., survived. The general results at Rothamsted and at Chiswick are con¬ 
sistent with those established by Professor Hoffmann, and combine to show that the 
survival of certain plants is due much less directly to external conditions than to 
the “ habit ” of the plant itself; that is, as already stated, to the facility the plant has 
of adapting itself to varying external conditions, and thus of triumphing over others 
less favourably endowed in this wise. 
The immediate source of victory lies very generally in the powerful root-growth of 
the survivors; including under the general term root, not only the root proper, but 
the offshoots and runners which are given off just below or on the surface of the 
ground. Indeed, this habit of growth is more advantageous to plants in such a 
struggle than the development of the true root downwards would be. 
With reference to these questions of struggle, competition, and association, it is 
requisite to distinguish clearly between those cases in which the competition or the 
straggle is direct, and those in which it is indirect. In some cases where plants grow 
in association the strong overpower the weak by virtue of their superior endowments, 
in others one plant gains the advantage because it was the first to take possession of 
the ground ; or because, for some reason or another, no resistance is offered to its 
spread. But, while among individual plants of the same species, having the same 
requirements and growing in association, there must necessarily be hostile competition 
which would disturb the balance of vegetation, and result in the survival of the fittest 
and the destruction of the weakest, there is also an opposite process which tends to 
maintain an equilibrium. Different plants have different requirements, and if these 
be supplied at the same time and place, the vegetation may be of a very mixed 
character, and no one plant or set of plants gain preponderance over the rest, till some 
circumstance arises to disturb the equilibrium. We have then to discriminate 
between the effects of hostile competition and those of peaceful concomitance or 
association. De Candolle, in the paper previously cited, asserts that all plants within 
a given area are at war with one another; but this assertion, in view of what has 
j ust been stated, requires to be taken in a qualified sense. 
We have already alluded to the fact that, in the case of various plants growing in 
association, the number of individual plants within a given area is generally small in 
