A R T O F G A R D E N IN G . P a r t IIL
2062. A ir is supplied by the portion of the atmosphere enclosed in the stracture.
This air may be raised in temperature, chai-ged with vapours, or renewed, at the will of
the operator. It might also be put in motion by ai’t, for the sake of obtaining strength
of stem in ramose or tree-like plants; but the motion communicated to plants, by opening
the cover, and exposing them to the direct influence of the air in fliie weather, is
deemed sufficient, either for this pui-pose, or for giving flavour to fruits when advancing
to maturity.
2063. S o il, it must he obvious, is perfectly within the control of ai-t, wliich, in fact,
can far surpass nature, when increased dhneiisioiis of the pai’ts of plants and improved
quality of fruit are objects.
2064. W a te r is equally at our command with soil: it may he made to pass through tho
house in a sui-face-rill; or under the soil in subten-aneons channels ; maybe retained
in a cistern or basin ; or introduced in tubes, either to throw up innumerable jets from
the floor, or pom- them down from the roof to serve as rain. It may be supplied
directly to the roots of plants, without wetting thcir leaves, in the manner of in-igation;
be stagnated round them, as in natural marshes; or made to ascend as vapour from
steam-pipes, by pouring it on flues or hot bodies, or even watering the floor or interior
sm-facc of the house. Having ascended, and fllled the air, it parts with its caloric, and
is precipitated on the plants in the form of dew.
S t j b s e c t . 2 . F o rm s o f Plant-houses.
2065. T he f ir s t p erm anent plant-houses w ere m e v d y chamhers with opaque roofs, and
only rather more glass windows than ordinai-y in front. In fact, houses of this description
were fi-equently used as banqueting rooms, when the plants were placed in the
open air during summer, as in the old orangery in Kensington Gardens. Houses with
opaque roofs, though totally unfit for plants during the summer, are still found in many
parts of the Continent, especially where they are wanted principally to afford a shelter
during the winter months; as it is found extremely difficult to protect plauts from the
severe cold in the northern parts of Eiu-ope when the roof is entii-ely of glass.
2066. Greenhouses w ith bonnet roofs were some of the __
first structures set aside exclusively for plants; and these are
still to be met with in Poland, and some pai-ts of the north of
Germany. In a house of this kind ( fig . 596.), the roof (a)
projects considerably over the steep glass front (b ), aud protects
the glass fi-om the hail. It also serves to protect the
plants from perpendicular frosts, but it deprives them of a
considerable portion of light and heat from the sun.
2067. T he plant-houses in the botanic gai-den at Nymphen-
burgh afford a specimen of a range of houses with opaque
roots at a more advanced period, and on a lai’ge scale. In
fig . 597., A is the groimd plan of the thi-ee hothouses and the greenhouse; B is the
general elevation; C is a section tbrough the palm-house; and D a section through the
central greenliouse, with the attendant’s house behind. In these houses the front glass
forms an angle to the horizon of 71° agreeably to the directions of Boerhaave ; and the
interior of the hothouse is heated by German stoves, concealed among the plants, and
sup{)licd with fuel from the sheds beliind.
2068. T he range o f plant-houses in the botanic gai’den at St. Petersburgh ai-e of the
same description; and as models for the construction of plant-houses in a cold climate,
it may be interesting to give the details of their constractioii and management.
2069. T h e hothouses in the Im p e ria l B o ta n ic G ard en a t S t. Petersburgh, of which a
general plan (fig . 598.) is given in page 590., were constructed agreeably to the following
principles; which are extracted from a paper which was lent us in Paris, in 1829, and
was said to have been drawn up by Dr. Fischer, the director of the garden. The best
exposure for hothouses, in cold countries, appears to be the S. S. E., or the S. S. E.
by S .; and in the north of Russia, on account of the cold and piercing north winds, it
is generally thought advisable to place them against walls or buildings, galleries or
corridors, in which, during winter, plants which do not require much light may be
placed; and in which certain vegetables, such as chicory, rhubarb, &c., may be forced ;
and mushrooms raised, or workmen lodged. - The depth given to hothouses, in the
north of Russia, is generally less than in other countries, unless the house requires to be
very lofty, in which case it is made aii’-tight, so as to preserve the heat. In the orangery
of the palace of Taurida, the roof being opaque, the ah- is kept warm by very few
stoves. When the hothouse is high, and the glass slopes considerably, care must bo
taken in constructing the front wall, so that it may not be thnxst out by the lateral
pressure of the sashes. Experience also shows that plants thrive in hothouses with the
glass sloping to different angles; it is, therefore, principally necessary to consider what
slope is best for throwing off the water, exteriorly and interiorly. The sashes may either
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