14 
INFLUENCE OF CLIMATE ON VEGETATION. 
correspondence and personal intercourse, which Mr. Herbert in the most kind and affable 
manner, allowed to go on for the last ten years of his useful life. He expressed an 
anxious desire that the point in doubt should be cleared up by a rigid course of experiments. 
This was in 1838, but although trials had then commenced, it was the end of 1845 before 
a final judgment was passed in my favour. Now, seeing that I am the party left to make 
the assertion, I do not wish any one to believe the result, but rather experiment for himself. 
Calceolaria, Fuchsia, or Pelargonium, will answer to make trials with, as being very easy 
to operate upon, and giving proofs in the second season. It is only necessary to be 
most scrupulous about the access of any pollen but the sort intended, and not to use a 
camel-hair brush to dust the pollen with. A brush that has been used more than once is 
little better than a lottery chance for experiments. Take two plants of the kind you fix 
upon — subject one of them to the worst treatment you can devise, after you dust the 
stigma, and the other just the contrary — in short any sort of treatment with its opposite 
will answer. I may, however, state the most severe trial that was made in the case 
referred to. Two scarlet Pelargoniums of one kind were planted out in rich compost under 
a south wall — the first two crops of flowers were cut off to give time for the roots to extend 
more freely. Then two of the strongest trusses of bloom on each were selected for the 
experiment, and all the rest were cut off, and also the shoots were stopped. A dozen 
blossoms on each shoot were impregnated with the same kind of pollen, and in a few days 
when it was ascertained that the pollen took effect — a truss from each plant was cut off 
with the whole length of the footstalks — these were put in a glass with damp sand under a 
hand-glass in the stove, where seven seeds ripened, the rest having died through this hard 
treatment. The two plants, with the other two trusses were petted as only experimentalists 
can understand. The produce of the whole is now three years old, and there is not the 
slightest variation perceptible among them yet. I believe, however, that sterility may be 
overcome in part, and some opposite characters may be stamped on seedlings, by peculiar 
treatment to the mother-plant previous to impregnation. 
INFLUENCE OF CLIMATE ON VEGETATION. 
By Mr. T. Moore , Cwrator of the Botanic Garden , Chelsea. 
It is a very usual matter among men, for opinions to run into extremes, and this is true 
not only as regards matters of mere opinion, but equally as regards matters of practice. 
From the influence of this common course of things, gardening is by no means exempt. 
We may assume that it is brought to bear in this way : — In propounding and supporting 
some great and indisputable principle, those who are looked to as authorities, are apt to use 
strong expressions, not perhaps beyond what the subject justifies, but yet sufficient to give 
the impetus to public opinion, which, once fairly started, like the snowball, gains weight as 
it progresses. 
It is proposed to apply these remarks to the subject of low night temperatures in 
hothouses, the principle of which is indisputably good, and the practice of which, both has 
been and is, extensively followed. Public attention has been recently directed very 
especially to this subject ; and as in similar cases, it is quite possible that public opinion 
concerning it, may be carried to an extreme. For this reason, it may be well to remind 
those “ whom it may concern,” that there is a limit which may not be safely passed, in 
decreasing the temperature allowed at night to the plants of tropical climates, under 
artificial treatment. Any plant may be killed by a certain decrease of temperature, and 
injured though not destroyed by a less amount of decrease, as surely as that any plant may 
be killed by a certain increase of temperature, and injured though not destroyed, by a less 
amount of increase. The influence is felt in different ways, but the general results — death 
or indisposition — are sufficiently correspondent. The influence, moreover, is felt in various 
degrees, according to the previous condition of the plant, but there is nevertheless a limit 
both to the increase and decrease of temperature, compatible with the safety of every plant. 
Now, it is within the limits thus marked out, that every plant attains its perfection ; and if 
the highest and lowest degrees of temperature that a plant will bear with impunity , be 
