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these statements are quite at variance with those generally believed 
concerning the Flora of tropical climates; but coming from the 
source they do, we can scarcely, I think, dispute their accuracy. 
Indeed, when we consider the subject, we shall find that such a 
result might naturally be expected ; for, amid the dense gloom of a 
tropical forest but little light can penetrate, and it is, as we all 
know, light which gives colour. Even in our own climate the 
colour of flowers is not so brilliant ceteris paribus in a dense wood 
as in an open plain. The idea of brilliant colour, especially 
appertaining to tropical flowers seems, as Mr. Wallace remarks, to 
have arisen partly from the fact that in this country tropical plants 
are generally grown in conservatories, where they are exposed to 
abnormal conditions of light. It would seem, perhaps, that 
while the tropical regions are far richer in the production of 
vegetable forms, so far as concerns brilliancy of colour, we have this 
advantage, that is the vegetation of temperate latitudes is more 
brilliant in hue than that of tropical regions. How are we to 
account for this? Partly, I think, as regards vegetation and the 
colour of flowers, by the following considerations, or perhaps more 
properly, suggestions. We know that the colour of flowers 
depends, in some measure at least, upon the amount of radiation of 
light. Now, there are three distinct classes of rays from the sun ; 
rays of light, rays of heat, and what are called actinic or chemical 
rays, which, combined with the others, are probably effective in the 
production of those chemical changes which all plants more or less 
undergo. It is, then, by the absorption and radiation of these rays 
of light that the colour of the flower is produced, and as in tem- 
perate climates, these rays seem to be in excess, while those of 
heat and actinism are subsidiary, especially, perhaps the former, 
the result seems to be that in such regions the colour of flowers is 
comparatively more brilliant than in tropical climates, where, besides 
the larger amount of heat and actinic rays and the smaller propor- 
tion of rays of light, the effect of these latter is possibly much 
counteracted by the greater amount of moisture present in the air. 
It also seems possible that the greater richness of soil which 
generally prevails in tropical climates, may be another reason 
of the comparative want of brilliancy in the flowers, for wherever 
the soil is light and dry, indeed, even arid, under the conditions of 
a clear blue sky and bright sun, we find the colour of flowers 
in proportion more brilliant than in certain tropical regions is the 
case. Coming to our own climate, we shall, I think, find that these 
suggestions are in some measure borne out; as for instance, in the 
generally brilliant colour of our wild flowers. It would seem, then, 
that a rich soil, combined with a damp atmosphere, and a larger 
proportionate amount of heat and actinic rays, has the effect of, as 
it were, deepening, and, perhaps, to a certain extent, fixing the 
