514 
THE GARDENING WORLD 
April 13, 1889. 
moisture necessary for fruit houses depend upon the 
subjects grown. Tomatos being semi-succulent in their 
nature, fertility in opposition to vegetative growth is 
greatly promoted by a dry atmosphere. This condition 
also greatly tends to check the progress of fungoid 
diseases, some of which are very destructive to Tomatos. 
There have been cases where the plants were almost 
ruined or killed by a virulent attack of the Potato 
murrain, or something closely allied to it, and whose 
career was stopped by a change from wet to dry atmo¬ 
spheric conditions. Both in this instance as well as in 
the case of Vines attacked with mildew, the use of the 
pyschrometer would prove a valuable friend as an 
indicator of the degree of humidity of the atmosphere 
to secure certain results. A saturated atmosphere is 
beneficial at times, inasmuch as it promotes a rapid 
extension of growth, while in the case of Vines and 
many other subjects it is of the utmost importance 
that the foliage should be dry for several out of every 
twenty-four hours ; and this is most advantageous 
during the middle of the day, so as to promote 
transpiration. Again, the degree of saturation of the 
atmosphere of a vinery during the rapid spread of 
mildew could be determined with scientific accuracy, 
and by altering the conditions it would check the 
disease, as in the case of the Tomatos mentioned. It is 
quite of common occurrence during moist, sunless 
weather in summer to see vineries kept close all day 
long, without ventilation either at top or bottom, 
simply that the requisite temperature may be kept up 
with the least possible expenditure of artificial heat. 
It is no wonder that the Odium finds in this a suitable 
atmosphere for its rapid development. The excess of 
moisture should be reduced by proper ventilation, even 
at the expense of more artificial heat or an actual 
lowering of the temperature, as great heat in sunless 
weather is productive of thin, flabby, improperly 
developed foliage, and the fruit prospects must con¬ 
sequently be less hopeful. I would suggest the use of 
hot-water pipes, to be laid along the lower part of the 
roof, to dispel moisture when required. 
When Vines as well as other subjects are 
being forced in winter, the question of high tem¬ 
perature is a very important one, and should not be 
ignored. Hard forcing of Vines in dull weather is 
productive of slender, weakly shoots, giving rise to 
bunches that frequently become aborted to mere 
tendrils, thus ruining the chance of a crop. Advice 
is often given against the practice of hard firing on 
frosty nights, even should the temperature of the 
forcing houses sink below the usually required standard. 
The reason is that the great difference between the 
temperature of the external and internal air causes an 
enormous evaporation of the moisture in the houses, 
and this is carried through the laps between the glass 
into the open air. During the long night while this 
state of matters is going on, the young and tender 
foliage is getting desiccated and injured by the aridity 
and heat of the atmosphere. Hence a lower tem¬ 
perature is advisable so as to reduce the excessive 
evaporation caused by the great heat of the pipes. 
Summary. 
To sum up the principal or leading points concerning 
the atmospheric conditions of plant houses, we have 
already noted that heat and moisture are intimately 
connected in their mutual relations towards any given 
class of subjects cultivated in plant houses, and that 
ventilation is necessary not only to modify these con¬ 
ditions, but to admit a free circulation of fresh air 
when the external and internal temperatures approach 
the same degree or are not widely different. Damping 
the paths and stages, as well as syringing, increases 
atmospheric vapour, and to a certain extent checks 
transpiration by saturating the atmosphere. This, by 
enabling the tissues of plants to become distended or 
gorged with water, promotes rapid growth or extension 
of plant tissue, which is not, however, synonymous 
with the manufacture of fresh material or an increase 
of weight, but merely an increase of bulk. Therefore, 
the atmosphere of plant houses must not always be 
kept in a saturated condition, but allowed to attain a 
certain degree of dryness during the hours of daylight 
in order to promote transpiration, or a rapid ascent of 
water from the roots towards the leaves of plants, and 
from thence into the air, for the simple reason that the 
amount of transpiration is a measure of the mineral 
constituents of plant food carried into the plant body. 
Assimilation of carbon from the atmosphere in the 
presence of sunlight can only proceed in a ratio pro¬ 
portionate to the smallest quantity of any absolutely 
requisite constituent to plant life that may be taken up. 
For instance, extension of tissue may proceed apace 
during darkness, or in the daylight, provided the 
atmosphere is saturated with moisture, but the plant 
may actually be losing in weight while that is going 
on. Promote transpiration and assimilation, how¬ 
ever, and you actually add to the dried weight of the 
plant. A builder could not advance his work by a 
superabundance of water when solid material becomes 
used up, neither can a plant add to its tissue without 
an adequate supply of carbon and mineral constituents. 
Besides the useful purpose of syringing and damping 
already mentioned, another valuable function recom¬ 
mending their use is the destruction of insect pests, 
such as green-fly, red-spider, and thrip, and the wash¬ 
ing of the foliage to prevent the accumulation of dirt, 
whereby a healthy performance of its allotted duties is 
prevented or retarded. In modifying the atmospheric 
conditions by means of ventilation, great care must be 
exercised in avoiding extremes of excessive dryness, or 
a rapid lowering of the temperature. The ventilators 
should be opened a little early in the day, and the 
amount gradually increased as the sun gains in 
strength. It is a gross mistake on the part of the 
cultivator to allow the temperature to run up very 
high with a saturated atmosphere, and then throw the 
ventilators wide open. A sudden rush of cold air upon 
plants in this condition is far more injurious to them 
than it would be on animals. Growth is checked by 
the paralysing of the functions of the leaves, and the 
plants become unhealthy, laying themselves open to 
the attacks of animal and vegetable parasites. Cul¬ 
tivated plants are under artificial conditions, and if the 
art, acting the part of a foster-mother, induces more 
rapid and greatly improved growth, it at the same 
time weakens the natural constitution of plants, 
rendering them subject to various evils. 
The psychrometer, far too seldom found in plant 
houses in this country, might often prove of invaluable 
service to gardeners if they could be induced to avail 
themselves of it, for the purpose of determining what 
degree of humidity is beneficial or prejudicial at any 
given temperature to plant life. Questions, such as 
the spot in Orchids, disease in Tomatos, mildew of the 
Vine, diseases of various subjects, and, in fact, the 
degree of moisture most beneficial to plant life in health 
and disease, might well be studied with the aid of the 
psychrometer. 
-- 
WATER, ITS USE AND ABUSE 
IN THE CULTIVATION OP PLANTS.* 
Where there is no water there is no life ; water, 
therefore, is absolutely essential to the life.and growth 
of a plant. The first stage of a plant’s life—the ger¬ 
mination of the seed—cannot take place until the seed 
has been permeated by water, and oxygen has converted 
part of the carbon into carbonic acid. Water also extends 
the tissues of the seed, and helps to dissolve the nutri¬ 
tious elements stored up in it, preparing it for the early 
needs of the germ when it commences to grow. Thus, 
in the first stage of the plant’s life it is stimulated into 
growth by the absorption of water. 
Plants are found to contain a great amount of 'water, 
as may be found by exposing them to a temperature of 
135° Fahr., which causes the water to evaporate, the 
plant or seed thus sustaining loss in weight to the 
following extent:—ripe seed 12 to 15 per cent., her¬ 
baceous plants 60 to 80 per cent., and many water plants 
and fungi as much as 95 per cent, of the whole weight. 
A plant cannot live in dry soil, w’ater not only being 
one of the most important elements of food, but it is 
also the vehicle by which foods in solution are carried 
into the plant, and which go to form the component 
parts thereof, 2,000 pounds of water passing through a 
plant for every pound of matter fixed. Water is taken 
up by the plant through the small root-hairs found a 
little above the apex by osmosis, and is carried through 
the plant assisted by growth and transpiration. There 
is also a pressure from the roots, drops of water often 
appearing on the margins and apices of the leaves of 
many grasses (especially striking in Maize) when trans¬ 
piration is diminished by the absence of light and the 
cooling of the air, while the activity of the roots is 
increased by warm, damp weather. 
Water and its Impurities. 
Absolutely pure water, made from the oxygen and 
hydrogen gases, is seldom obtainable, and would be of 
little value. Distilled water is a near approach to pure 
water, but of no use. Rain water, it must be noted, is 
First-prize essay on the subject of watering, gained by Mr. 
James Macfarlane in the Chiswick Gardeners' Mutual Improve¬ 
ment Association competition, 1SSS. Prizes offered by Mrs. 
S. A. Lee, Arlington Park Villas, Chiswick, to be competed for 
by members under the age of thirty. 
by no means free from impurities, for it absorbs many 
chemicals from tbe air while falling, the ingredients 
differing in different localities, according to what 
factories, &c., exist in tbe neighbourhood. Such 
chemicals as nitric acid and carbonic acid, also metals 
as iron and magnesia, are absorbed. River water varies 
a great deal, it being made up of rainfalls and springs, 
and is influenced by the bed over which it flows. That 
flowing over flint or granite beds is purest and tolerably 
soft. 
The hardness of water is generally caused by chalk 
which it contains in solution. This chalk is not 
beneficial to plants, and when used through the syringe 
leaves a white deposit on the leaves. By exposing the 
water to the air, a portion of carbonic acid is given off, 
and a corresponding amount of chalk deposited. A few 
grains of pure brisk quick-lime stirred into each gallon 
of water would soften it, without adding a particle of 
lime to the fluid. Gypsum or sulphate of lime also 
hardens water, and sometimes exists to such an extent 
as to destroy the bottoms of cisterns containing it. 
Rain water is undoubtedly the best for general purposes, 
and should he stored up in large reservoirs or tanks 
during the rainy season. 
On the Proper Application of Water. 
After we have obtained the water, its application is of 
the greatest importance, and it needs all the skill and 
discretion possible on the part of the operator. The 
quantity a plant demands depends on its nature, 
structure, and surroundings, evaporation going on to a 
much greater extent in hot than in cold weather, and 
on light than on heavy clay soils. Watering indis¬ 
criminately must be strictly avoided—judgment must 
he exercised, and the circumstances taken into con¬ 
sideration. For instance, although no hard-and-fast 
rule can be laid down, it may be taken for granted that 
the smaller the roots, the more constant must be the 
supply of water, from the smallness of the agents about 
to receive it. Such plants are most impatient both of 
drought and over-watering, while those with large roots 
and succulent leaves are less affected by the former. 
Rapid growth indicates need for a continuous supply of 
moisture. Most water is wanted in the growing season, 
less when flowering, more again when fruiting, and 
very little when seeding. Hence fruit trees, Apples, &c., 
during a dry summer should have a good soaking or 
two, and mulchings to prevent evaporation. This 
watering should be thorough, in order that the ground 
may he permeated with moisture. The evils of surface 
watering are greater than one would generally suppose. 
July will be about the month to commence the watering 
operations above referred to, the winter rains supplying 
the moisture for the growing season. It is also better 
done during dull weather ; evaporation not going on 
so rapidly, and the earth being cooler, the plants will 
be in a kind of prepared state for receiving water. 
Vine borders need special drenchings when the fruit 
is swelling, there being a great demand on the roots. 
The mildew on Vines is generally caused by misplaced 
moisture, dryness of the border, and too much atmos¬ 
pheric moisture in the house. It may here he observed 
that an excess of moisture will do more harm than 
good by destroying the quality of the fruit; so that the 
rule would he to water fruit trees when swelling, but 
not when ripening their fruit, the maturing being 
really the seeding period. The Melon is an exception 
to this rule, as it requires abundance of moisture 
throughout the whole of its growth, acquiring the 
greatest excellence in countries where its roots are 
immersed in water, as on the floating islands of 
Cashmere, the irrigated fields of Persia, and the spongy 
river beds of India, but these Melons have an enormous 
perspiratory power, arising partly from their large 
surfaces and the intense heat. Still, not having the 
same degree of heat in this country, the water must be 
diminished, as they lose quality in flavour if the roots 
are immersed, as proved by experiments in the Royal 
Horticultural Society’s Gardens. The Lettuce also 
requires an abundant supply throughout its whole 
growth, to keep the leaves tender. 
That transpiration goes on to a considerable extent 
in land plants, as in the Melon, may be seen by placing 
a plant under a glass case, when the latter will soon 
become dewed all over ; also by cutting off a shoot and 
placing it in a bottle full of water, tightly sealing the 
mouth. If this be placed under a glass case the water 
will be seen to gradually decrease from the bottle, and 
a deposit will he made on the glass. Dr. Hales found 
that an ordinary-sized Cabbage in twelve hours evap¬ 
orated water to the amount of 19 ozs. The same 
gentleman made experiments with the shoots from 
Apples, Pears, Apricots, Peaches, and Cherries, by 
