8 
STEAMING FORCING HOUSES. 
have rendered incapable of being absorbed; the quality of the pro¬ 
duce under such circumstances is invariably deficient in flavour, al¬ 
though its appearance may be much finer than those grown under 
different treatment. Much depends on the purity of the air of a 
hothouse, and all damp air becomes much sooner contaminated than 
dry. When we fill a house constantly with steam we prevent the 
plants in it, discharging their fluids according to the process of nature, 
and consequently do them serious injury, every glass roof, from its 
confining so many unwholesome vapours, may be rightly considered 
a trammel to nature. How much every greenhouse exotic is bene- 
fitted in the autumn by cool dry treatment, we know by experience; 
the same rule ought to he observed in every department. Heat com¬ 
bined with too much water tends to debilitate and paralyze the en¬ 
ergies of plants, we may obtain the object we wish, but it is at the 
risk of a failure the succeeding season, the wood leaf and parts of fru- 
tification are affected, and the petals not unfrequently expand of a 
pale colour and speedily fall off; this does not arise from the treat¬ 
ment of the present season, but of the preceding one, and there is 
no doubt but the whole constitution of the plant is entirely different 
from what it would have been under other treatment. Notliing is 
more opposed to nature than steaming in the morning; if the wea¬ 
ther is cloudy there is no necessity for it, if on the contrary, the 
effects are exceedingly pernicious. The sun never appears without 
giving notice, and allowing time for vegetation to dry, and be pre¬ 
pared for its reception. I stated in page 295, volume 1, that I be¬ 
lieved nothing tended so much to bring metallic houses into disre¬ 
pute, as the close manner in which they were glazed, entirely pre¬ 
venting the steam and vapours escaping, and the air of the house 
becoming dry, and I still think if a contrary course was pursued, 
few or none of such houses would ever be found to fail. Nature as¬ 
signs a sufficiency of moisture for vegetation in the common atmos¬ 
phere, and if we administer above this portion, the effects become 
injurious both to present and future crops; the quantity of vapour 
which arises in one of the dryest houses is very great, particularly 
where a number of exotics are kept and daily watered. If we ob¬ 
serve the openings or laps of the squares in the evening, when there 
is a current of air acting upon the roof, how quickly the vapours are 
replaced, after being removed. I fear many persons keep a more humid 
atmosphere than they otherwise would, because they conceive it a 
preventative against the red spider, a remedy for which I will shortly 
forward you. There is no doubt but the orchard crops as well as 
other fruits are more affected by a wet dark autumn, than by the 
