182 
ON THE INFLUENCE OF CLIMATE ON PLANTS. 
this nature, which have not a direct practical tendency, we do not intend to deviate 
from our usual course in this instance ; and as we have, in a former article, shown 
the influence of light on stove plants, accompanying our remarks with useful 
directions for their general management in this respect, we now propose to extend 
our observations to those singular objects which are usually termed " succulent 
plants but, as it will not be convenient here to detail the numerous genera which 
are comprised in this term, we shall select the tribe Cactce, and the genera Mesemhry- ~ 
anthemum and Agave^ as types of the rest, and severally consider these with refer- 
ence to the subject of light. 
We have previously stated, that plants which are of a succulent or juicy sub- 
stance require a great degree of light, and are usually found growing in very 
exposed situations. The numerous species of Cactce which are now cultivated in 
our collections are nearly all met with on dry open plains, and seem to be provided 
by nature for the sustenance of man and animals in those districts where other 
kinds of vegetables could not exist, and where neither food nor water can be pro- 
cured from any other source. It is not a little remarkable, that plants of a 
consistence so watery as those now under consideration, should be found in such 
localities as we have above mentioned, and be able to endure the scorching rays of 
a meridian sun with perfect impunity ; but this may be accounted for by their 
having an exceedingly limited number of pores or respiratory organs, so that while 
they are furnished with organs of absorption to collect all the moisture which can 
possibly be obtained from the parched soil, they are thus enabled to retain it to 
such an extent as constantly to preserve them in full health and vigour. M. de 
Candolle states that various species of Opuntia are planted by the natives of the 
surrounding country in the crevices of the old lavas at the base of Mount ^Etna, 
in which situations they flourish in such extraordinary luxuriance, as eventually to 
break up the lava into mere fragments, and likewise produce an immense quantity 
of fruit ; a striking proof of their capability of sustaining a great intensity of drought 
and solar light. Besides the above, it is well known that Cactce grow naturally in 
those localities where they are constantly exposed to the most powerful influences 
of a tropical or equinoctial sun ; and we may from thence reasonably infer, that 
unless our treatment of them in this respect is assimilated as much as possible to 
that which they receive in their natural situations, no satisfactory results will ensue 
from it. Most good cultivators of Cactce have the whole of their succulent plants 
collected together in one house ; and this system is productive of many important 
advantages ; for, when kept along with a collection of stove plants in the stove, 
independently of the degree of heat and moisture being injurious to them, they 
cannot be supplied with a sufficient quantity of light. A few years ago, we had 
the whole of our collection of succulent plants placed in the stove ; the consequence 
of which was, that owing in a great measure to the deficiency of solar light, as 
well as to the superabundance of moisture, we lost many of our most valuable 
species, particularly of Stapelia^ which in some instances perished in a few days 
without evincing any previous signs of decay. We therefore found it necessary to 
