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wliicli that usually rises from the ground, as I could obtain i t ; and little or no artificial
heat was given dining the night, unless there ajipearcd a prospect of irost. Under this
mode of treatment, the blossoms advanced with very great vigour, and as rapidly as I
wished them, and presented, when expanded, a lai-gcr size than I had ever before seen of
the same varieties. Another ill effect of high temperature during the night is, that it
exhausts the excitability of the tree much more rapidly than it promotes the growth, or
accclcratcs the maturity, of the fru it; which is, in consequence, ill supplied with nutriment,
at the [leriod of its ripening, when most nutriment is probably wanted. The muscat of
Alexandria and other late grapes are, owing to this cause, often seen to wither upon the
branch in a very imperfect state of ma tu rity ; and the want of richness and flavour in
other forced frnit is, I am very confident, often attributable to the same cause. There
arc few peach-houses, or indeed forcing-houscs of any kind in this country, in which the
temperature docs not exceed, during tíie night, in the months of April and May, very
greatly that of the warmest valley in Jamaica in the hottest period of the year; and there
ure probably as few forcing-houses in which the trees arc not more strongly stimulated
by the close and damp air of the night, than by the temperature of the dry air of the
noon of the following day. The practice whicli occasions this cannot be rig h t; it is in
direct opposition to nature.” (Hort Trans., vol ii. p. 130.)
2637. Air. Knight considers that gardeners often and widely c i t , “ by too freely
admitting the extenial air during the day, particularly in bright weather. Plants generally
grow best, and fruits swell most rapidly, iu a warm and moist atmosphere ; and
change of air is to a very limited extent, necessary or beneficial. The mature leaves of
plants, aud, according to Saussurc, the green fruits (gi-apes at least), when exposed to the
influence of light, take up carbon fi-om the surrounding air, whilst the same substance is
given out by evei-y other part of the p la n t; so that the purity of air, when confined in
close vessels, has often been found little changed at the end of two or three days by tbe
growth of plants in it. Bnt even if plants required as pure air as hot-blooded animals,
tlic buoyancy of the heated air, in every forcing-housc, would occasion it to escape and
change as rapidly, and indeed much more rapidly, than would be necessai-y. I t may be
objected, that plants do not thrive, and that the skins of grapes are thick, and other fruits
without flavour, in crowded forcing-lionses ; but in these it is probably light, rather than a
more rapid change of air, that is wanting. When fmits ajiproacli to maturity, such au increase
of ventilation as will give the requisite degree of dryness to air ivithin the house,
is highly beneficial ; provided it be not increased to such an extent as to reduce the temperature
of the house much below tho degree in which the fruit has previously grown,
and thus retard its progress to maturity. The good effect of opening a peach-liousc, by
taking off the lights of its roof, during the period of the last swelling of the fruit, appears
to have led many gai-dcners to overrate greatly the beneficial influence of a fi-ee current
of ail* upon ripening fruits ; for I have never found ventilation to give the proper flavour
01- colour to a peach, unless that fruit was at the same time exposed to the sun without
the intervention of glass ; and the most excellent pcaclies I have ever been able to raise,
were obtained under circumstances where change of air was as much as possible prevented,
consistently with the admission of light (without glass) to a single tree.”
2638. Water. The supplies of water given to plants sliould be regulated by the supplies
of heat, the natui-e of the plant, its state in regard to growth, and the object for
which it is cultivated. Abundance of heat should generally be succeeded by copious
waterings, unless the nature of the plant, as its succulency, or its doi-mant state in regard
to gi-owtli, render that improper. Plants cultivated for thcir fruits should be less
watered during the ripening season than such as are grown for their effect; a cli-y atmosphere
being most conducive to flavour. Tho succulent shoots of trees, K night obsciwes,
always appeal- to grow most rapidly in a damp heat during the n ig h t; but it is rather
elongation than growth which then takes place. The spaces between the bases of the
leaves become longer, but no new organs are added ; and the tree, under such circumstances,
may with much more reason be said to be drawn, than to grow ; for tlie same
quantity only of material is extended to a greater length, as in the elongation of a wh-o.
S e c t . VI. Operations to imitate warm Climates.
2639. The imitation o f warm climates hy hothouses must not be confounded with the art
of forcing the vegetables of temperate climates into the premature production of tlieir
flowers or fruit. The former was the first object for whicli hothouses were erected ; and
conservatories, greenhouses, and plant-stoves existed in this country before any description
of forcing-houses; even pineries are of subsequent introduction to botanic and ornamental
hothouses. The various climates and constitutions of plants require atmospheres
of different degrees of temperature and moisture; but experience has proved, that the
plants of every warm connti-y in the world may be grown in one or other of the three
following descriptions of hothouses: — 1. The greenhouse, of which there ai-e several
%
varieties, as for example, the heathery, the geranium house, the camellia house, the
orangci-y, the Cape house, the Australian house, See,., besides the conscn'atory, in wliicli
tlie plants are inserted in the soil witliout pots, and the cold-l'ranie for bulbs. 2. 'The
dry stove, for succulent plants, or such as require a dry atmosphere; and 3. The moist
or bark stove, inclnding the palm house, the orchideous house, and the house for those
tropical [ilaiits wliich require the highest degree of heat, and an atmosphere moist in
proportion.
2640. Treatment common to the three species o f artificial climates. In general, exotic
plants are kept in p o ts ; but in some cases, fruit-bearing plants, as the orange ; plants
with large roots, as the strclitzia ; and luxuriant creepers, as the different passifloras, are
planted in the ground. The soils arc, of course, very various, and can only be treated of
with advantage under each species, tribe, or family. There are none of them, however,
that ivill not thrive either in peat earth mixed with sand, or loam, or in a mixture of
these. For pines, oranges, and lai-ge-blossomed plants, rotten leaves or old cow-dung are
added with advantage, and to some of these, as to the orange and the pine-apple, liquid
manures are frequently applied. Gardeners in general are averse to the application of
any thing rich to the soil of exotic plants which are not cultivated for their fru it; a prejudice
evidently contrai-y to analogy, and originating, iu all probability, in the circumstance,
that it is in general desirable to keep exotic plants small, both for want of room
in ordinary-sized houses, and by that means to induce a flowering state. Now, liowevcr,
when the facilities nf hothouse building by wrought and cast iron, and the cheapness of
glass, admit of covering several acres of ground with a glass roof at 50 ft. or 100 ft., or
a t any distance from the surface; and when the mode of heating by hot ivatcr or by
steam readily admits nf keepmg such a space at any required tcmperatiire, all exotic
plants, where expense is not an object, may be planted in groimd which lias been duly
prepared, cultivated, and manured, like a slirubbery, whore they may be allowed to attain
thcir natural size. With the exception of temperature, the operations in imitation of
artificial climates are the same as those for forcing ; we shall, therefore, confine ourscli'cs
to indicating the temperature of the three leading departments.
2641. The greenhouse is freely exposed to the infiuence of onr atmosphere when the
open air is not colder than 48° of Fahrenheit, and when winds and rains do not prevent
the opening of the roofs or other means of ventilation. “ As long as the weather continues
fair ivithout frost,” says Abercrombie, “ open the greenhouse windows in the
daytime an hour after sunrise, and close at the same time before sunset. Never admit
air by tbe door or sashes in foggy or damp weatlier, or when bleak cutting winds prevail.
The admission of air in the middle of a clear frosty day will not hurt the plants,
if counteracted by fire-hcat. Admit air freely when the external temperature is at
42° by Falirenlicit, or above ; admit it guardedly when between 35° and 42° ; but not
at all when under 35° before tlie furnace is cmiiloycd.” Grcenlionsc plants arc generally
placed in the open air during the five mildest months in the y e a r; either by taking
off the roofs of the houses when these arc movable; or by removing the pots, and placing
them in the open gai-den.
2642. Dry-stoves arc opened night or day in the summer season, but only during
sunshine in winter and spring ; beginning, as in tlic forcing-houscs, by opening the top
sashes or ventilators first, by ivhich the external air descends and cools down the temperature,
partly by mixing ivith the internal air, and partly by forcing it out. Afterwards,
when the temperature of the atmosphere is above 50°, the lower or front sashes or ventilators
may be opened ; by which means a regular circulation or breeze is promoted in
eveiy part of the liouse, if a detached house; and in most parts of it, if forming part of a
range of connected houses.
2643. Moist or bark stove. The range of temperature which bark-stove plants can endure
“ is fi-om 63° to 81° of Fahrenlicit, the instmmcnt being in the middle of the house, at a
considcrabie distance from the furnace, and out of the reach of the sun’s rays.” According
to Abercrombie, the temperature by artificial heat of the bark-stove “ is 58° min., 70° max.
When meridian summer is felt, the temperature must keep pace with the increase of heat
in the atmosphere; and therefore will ascend, through all the intermediate degrees, to 75°,
80°, 85°, 90°, 95°, and even 100°. The maximum heat in the house, in Ju ly and August,
may in general be kept down to 90°, by free admissions of air, and by evaporation tfoni
the water given to the p la n ts ; although the force of the season will sometimes prevail to
95° and 100°.” M‘Phail, however, found that pines will bear ivithout injury 130°, and
he considers that no plant whatever will be injured by 120° . “ It is not uncommon to
give air to a hothouse only tlu-ough the day, and to shut it up close at night, perhaps
even increasing the temperature in the evening. Judicious horticulturists reverse the
practice. Knowing, for example, that, in the West Indies, chilly and cold nights usually
succeed to the hottest days, they rather imitate nature, by shutting up the liouse during
the day, and throwing it open at night. This practice, however, can only be followed in
our climate in the summer and autumn seasons.” (Neill, in Ed. Encyc. art. Hort.) This
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