February It, 1889. ] 
JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 
135 
&c.,” he considered most conducive to the health of plants breathing it. 
Most gardeners know that an atmosphere of a house impregnated with 
carbonic acid gas is impure and wholly unfit for animals to breathe. 
They also know that the case is different with plants, as carbonic acid 
gas and ammonia are generally present in the atmosphere of plant 
houses in varying quantities. But the leaves of the plants have a 
tendency during the daytime to absorb the carbon dioxide in the air, 
decomposing the same, and assimilating the carbon, which is one of the 
principal constituents of all vegetable structures, and setting free the 
oxygen. Plants may thus be said not only to breathe, but also to feed 
on this gas, and by so doing restore the equilibrium of the atmosphere 
destroyed by the exercise of the functions of animal vitality. It is 
also an indisputable fact that the respiration of fresh air during all 
favourable opportunities is absolutely necessary to the health of plants, 
notwithstanding the fact of your correspondent having pronounced the 
winter ventilation of plant houses as being both “ unscientific and un¬ 
necessary.” 
I assure Mr. Coombe that I have read his remarks on this subject as 
they appeared in print, especially in reference to his advocacy of a day 
and night temperature of 60° for Cucumbers during the early part of 
winter. Here, then, are his own words (p. 661). “ Our only weakness 
for a fixed temperature is shown in the endeavour to maintain the 
temperature as near 60° as possible both day and night.” Your corre¬ 
spondent boldly asserts that if an internal minimum atmospheric tempe¬ 
rature of from 65° to 70° is maintained in the Cucumber house during 
very mild and dull weather, when the external temperature ranges from 
50° to 55°, as is not unfrequently the case in November and December, 
“ heavily charged with moisture,” it must necessarily be a “ hot and 
moist” one. Nothing of the kind, as it requires very little warmth indeed 
in the hot-water pipes to raise the heat in the house to the temperature 
indicated under the conditions specified. Were Cucumber plants grow¬ 
ing in a temperature thus produced, freely, or indeed lightly, syringed, 
they would assuredly become a prey to the ravages of mildew. But 
the case is widely different when hard firing is necessary to produce and 
maintain the minimum temperature mentioned above during severe 
frosts. The conditions under which the same degree of heat is produced 
are so different as to render the syringing three times a day—the last 
time before banking up the fires—necessary, not only in order to promote 
a genial atmosphere, but also to ward off the attacks of red spider. In 
this case, although the temperatures are the same as those produced with 
but little artificial assistance, the air of the house may be fairly desig¬ 
nated “ hot and moist.” In the former case, and under the circum¬ 
stances indicated, the air had taken up as much water gas as it could 
contain at the existing temperature ; it therefore refused to take up any 
more, and evaporation ceased, so that under these circumstances to 
distribute moisture in the house, otherwise than applying it to the roots 
of the plants when considered necessary, would be assuredly both “ un¬ 
scientific and unpractical,” and would be followed by the appearance 
and rapid spread of mildew, provided immediate steps were not taken to 
arrest its further progress, by dusting the affected leaves with flowers of 
sulphur while damp, and maintaining a dry and warm atmosphere, a 
little fresh air being admitted to the house. The capacity of the air for 
taking up water gas varies with its temperature, increasing as the latter 
rises, and vice versa. 
Now a word in reply to Mr. Bardney’s criticisms, to many of which 
the foregoing remarks will apply. So far as my experience goes all 
recently erected houses for the production of winter Cucumbers have 
been constructed as near as possible on the air-tight and heat-economising 
system, the “ keyholes ” being protected by the usual escutcheon. I 
have several such forcing houses here, and I always embrace favourable 
opportunities to admit a little fresh air to the plants for from a quarter 
of an hour to an hour’s duration, according to circumstances, in the 
hottest part of the day during the winter and earlv spring months, air 
being given, of course, more plentifully, and for longer intervals in the 
summer and autumn months, with a “ chink ” left on at night, putting 
it on about 8 p.m. and taking it off at 6 A.M., except in the case of 
houses containing ripe and ripening fruit, when the houses are damped 
down and kept close for an hour and a half or thereabouts. I do this 
because I am convinced that the admission of fresh air, according to the 
state of the weather and the particular stage of growth at which the 
occupants of the several houses may have arrived, is necessary to the 
well-being of the plants, and because, moreover, I feel sure that pent-up 
air for several hours at a time is unnatural and injurious to plant life, 
particularly so to the proper colouring and flavouring of fruit. 
Mr. Bardney is the only one who has said anything in this discussion 
about admitting “ large volumes ” of fresh air into the Cucumber or any 
other forcing house during the interval from January to April. No 
practical man would for a moment ever think of doing such a thing. 
There is a wide difference between opening the ventilators to such an 
extent as to admit the least possible quantity of fresh air, and in admit¬ 
ting “ volumes.” Moreover, the hot-water flow pipes run parallel to 
and within a couple of inches of the ventilators, thereby warming the 
fresh air as it enters the house. All practical gardeners are guided 
nearly as much by external as they are by internal conditions in the 
management of their forcing and other houses ; indeed, the latter is 
regulated to a great extent by the former. With regard to Mr. 
Bardney’s reference to “ pushing the winter Cucumber plants into 
growth during mild weather by giving them a night temperature of 60° 
to 75°,” this is certainly a great leap, and affords ample scope for a 
fluctuating temperature playing fast and loose with the health and vigour 
of the plants. In admitting the enormous latitude afforded by his 
figures he says, " Let us examine it, and see if external conditions do not 
justify such a course.” In what way, I ask 1 and he replies, “ If the 
outside temperature falls to 25° the inside temperature is 60°, allowing 
a difference of 35°. If it stand at 45° outside, and the maximum inside 
is 75°, we have a difference of 30° ; ” adding, that “ natural conditions 
warrant such a course, or even a higher night temperature than I have 
named.” What natural conditions does Mr. Bardney refer to ? Pre¬ 
sumably he means the external conditions of the weather as compared 
with the internal temperature of the Cucumber house, and not the 
natural and most favourable conditions under which the plant is found 1 
growing in the warm countries of Asia. In arranging his external and 
internal temperatures, and ascertaining the difference between given- 
degrees of heat in both cases, he appears to have taken no trouble to find 
out whether his arrangement coincides with those existing in the native 
habitat of the Cucumber plant during its season of growth. This should 
be the first consideration in the culture of all exotic plants and fruits. 
If the best results are secured from Cucumber plants growing naturally 
in a minimum temperature of, say, 70°, what justification can Mr. 
Bardney find for fixing the minimum night temperature at 60° to 75° in 
accordance with the whims of the weather, if he has the means by which 
to produce and maintain the necessary degree of heat and moisture ? I 
write on a label attached to the thermometer in the Cucumber house, 
night temperature 65° to 70°, according as the weather is cold or mild ; 
70° to 75° by daytime, with fire heat, running the temperature up to 85° 
or 90°, whenever we get the chance to do so with sun heat, plenty of 
atmospheric moisture at that temperature being distributed in the house 
when the slightly opened ventilators are closed between half past twelve 
and one o’clock in the afternoon. 
Every gardener having houses erected for the forcing of plants, 
fruits, and flowers during the winter and early spring months would, as 
a matter of course, have them constructed on the “ air-tight ” principle, 
in order to keep out the cold as well as to lessen the necessity for the 
application of artificial heat, allowing him at the same time the means- 
of admitting whatever quantity of fresh air be deemed necessary. 
Experienced men having badly glazed houses for the production of 
winter Cucumbers will not for a moment think of opening the ventilators 
for the purpose of admitting fresh air, they being already conscious of 
a too constant and liberal supply of that element passing through their 
houses. In the summer this constant current of fresh air in the houses 
would be beneficial rather than otherwise for the plants. 
In other words, your correspondent implies that the method of 
procedure adopted by me in the culture of winter Cucumbers is 
unnatural. Let us see, then, whether the modus operandi which I have 
practised and recommended for several years past justifies such a 
conclusion. Our winter-bearing Cucumber plants are raised from seed 
sown singly in 3-inch pots the end of August. These are planted out 
as soon as they are large enough in narrow borders having two 4-inch 
hot-water pipes underneath for supplying bottom heat to the roots. 
They are growing steadily during September, October, and November, 
giving plenty of air on all favourable occasions and liberal supplies of 
tepid water at their roots as the latter increased in permeating the soil, 
keeping all flowers picked off as soon as they appeared and the shoots 
trained thinly over the trellis, the obvious object being to get the trellis 
duly covered with short-jointed consolidated growth, and the soil in 
which the plants are growing a network of roots by the time we require 
the plants to yield a constant supply of shapely crisp fruit. To 
produce and maintain this from the time the autumn-bearing plants are 
dispensed with (usually the end of November) until the middle or end 
of May ; when we require the house for Melons we aim at a night 
temperature of from 65° to 70°. I leave the readers of the Journal to 
say whether this practice i3 sound or “ unnatural,” and also to say that 
the Cucumber being a moisture and heat-loving plant it is, or it is not, a 
mistake to keep it too cool or dry ; and also to say whether if the fruiting 
plants are subjected to a minimum night temperature of 60° for a 
fortnight at a time, the external temperature being about 25°, the result 
will, or not, be poor. As a fact, fruit thus produced cannot be other¬ 
wise than tough, distorted, and of bitter flavour. 
In the matter of giving air Mr. Bardney says, “Young men cannot, 
and never will, carry out the instructions of their chief on this point.” 
He fails, however, to adduce any practical reason showing why they cannot 
do so if they try, and provided the head gardener writes on a label 
attached to the thermometer in each house the temperatures he desires 
to be kept up therein day and night under stated conditions. Without 
some guide of this sort young men cannot be expected to always 
remember the temperatures and the conditions on which they are based 
that are to be observed in the forcing and other houses. The system has 
been in practice here for several years, and has been attended with very- 
satisfactory results, watchfulness on the part of the young men whose 
duty it is to attend to the ventilation being all that is required. 
One word more on ventilation. Mr. Bardney says, “ The ‘ chink ’ of 
air business if practised by all sound practical men for plant and 
Cucumber houses during the winter is certainly a ‘ fad.’ Fads invariably 
form a very sma'l minority in the gardening communities. Let us see 
what position they occupy in reference to the present subject—namely, 
the necessity for admitting fresh air to Cucumber houses, &c., in winter. 
The Journal of Horticulture in its calendarial directions for December 
6th (the same issue in which my brief note on winter Cucumbers 
appeared), p. 525, says, “ Keep the day temperature at 70° to 75°, being 
very careful in the admission of air, though a little should be given to 
clear the glass of condensed moisture and Mr. W. Coleman advises 
in a contemporary the giving of a little air at 76° if only for half an. 
