i&5^; 
VEGETABLE PHYSIOLOGY. 
August mid September. — ^NigM temperature, from 55 to 60 degrees. By day 20 degrees more. Remove 
the plants to pits, or a sheltered situation. Withhold water, and give the plants the full glare of day. 
If they are out of doors, lay the j)ots on their sides. AVhen the wood is brown and fh-m, and growth 
stopped, cut the jjlant well in, giving due attention to keeping the pjTamidal shape ; and if the shoots 
at the base are cut to about seven inches, or flush with the pot, it will be right. This is the resthig 
period. But we would greatly recommend to steal a march at this period, and try to have the plants 
fuUy matured, and cut back in August. By the end of September, the young shoots will be appearing. 
Lift the pot, syringe, and give them the benefit of night dews, without watering the ball. Shift the 
plants, and induce to grow fi-eely. 
October and November. — Temperatm'e decrease with the season — from 55 to 40 degi'ees at night. 
H the plants are not shifted, do it early, by shaking away the old soil, slightly pruning the roots, and 
using say an 11-inch pot. The soil must be lighter than before, less rich, perfect di-ainage, also 
some bits of charcoal mixed with the soil. A catei'piUar infests the plants at this period — keep watch- 
ing and hand-ijicking it. Take every advantage of sunny days, and dewy nights ; but frost must be ^'igi- 
lantly guarded against from the middle of October. A luxuriant growth is not, at this period, desir- 
able, but a healthy, short-jointed, and vigorous break or push, which must be kept in check until the 
end of January. Do not excite the plants now in any way. 
December and January. — Night temperatm-e from about 35 to 40 degrees. Day fr-om 5 to 10 degi'ees 
more. Avoid using much water. In severe weather the house or pits should be covered at night 
by mats or shutters. Tliis wiU economise the fuel, and save the energies of the plants. About 
the beginning of the year the plants may be finally shifted, the house whitewashed, and the tempera- 
tm-e sUghtly increased, advancing afterwai'ds with the season. By fair management you may expect 
a fine display in time for the June shows of 1851. 
iirgrtnlilr ^^IjtjsinlDgii. 
By AUTHUH HENFEEY, F.L.S., LECTUjtEE, on Botany at St. Geokge's Hospital. 
INFLUENCE OF HEAT AND LIGHT. 
IWIHE remaining physical forces which we have to consider are those of heat, Ught, and, above all, 
21 chemical affinity. I do not include electricity here ; since, althoagh it must be supposed to exer- 
cise a veiy important agency over vegetables, as well as other material bodies, we are at present 
wholly without satisfactory data as to the occm-renee of electrical jihenomena in plants. The various 
cmde specidations which have occasionally been presented in reference to this subject, appeal', in 
most cases, to have originated in a very imperfect knowledge both of the ascertained laws of electi'i- 
oity, and of the structm-e of plants themselves. It is certain that in those few experiments where 
I portions of plants (in wluch the vital cu-culation can be watched, as in the Chara,') have been examined, 
I while within the influence of artificial electrical and magnetic arrangements, no interference has been 
observed ; while the destruction of trees by hghtning would seem to prove that they are bad con- 
j ductors, ofiering some obstacle to the passage of the electric fluid, which then, instead of ti-aversing 
j them freely, as it would a metallic conductor, rends them asunder. Since we know chy wood to be a 
bad conductor, we must suppose the fluids of living plants to be the cause of any conductuig power 
they may possess, and how the general electricity of the atmosphere may affect the operations goiug 
on in these fluids, we are as yet altogether ignorant. 
The effects of heat are too well known to requii'e that we should dwell upon them to any extent 
here ; I wiU merely remark that, in endeavom-ing to imitate the variations of climate by means of 
artificial heat in cultivation, we must always bear in mind that light also takes a very important sliai-e 
in producing the difierences in the vegetation of different zones. I may allude also to some recent 
obsei'vations on the causes of the distribution of plants, which bear reference to practical points. It has 
been shown, vdth a great degi-ee of plausibility, that plants have pecuUar constitutions, if we may so 
express it, in regard to heat ; that is to say, that each species of plant seems to require a certain 
amount of heat within its season of active vegetation. Thus, an annual plant, which runs fi-om 
the state of seed to its own seed-bearing period and death, in six months, in one climate, may pass 
through the same com-se of existence in shorter spaces of time, in proportion as the climate in which 
it gi-ows is hotter. Moreover, plants adapted to different regions appear to have specific fixed points, 
below which they are, practically speaking, at rest; and thus, although they may require only a certain 
whole amount of heat for each season, may require to he always at a high temperature, and thus spread 
then- gi-owth over a shorter space of time. For example, if a plant wfll begin to vegetate with us at 
our March temperatm-e, and last till October, the same plant may grow and pass through all its stages 
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