398 
JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 
( May 17,1888 
qiiently decided to extend it to Friday evening, and an ample 
opportunity will thus he afforded to all who are desirous of visiting 
a beautiful and extensive display of plants and flowers. The 
groups of Covent Garden Market plants will be specially 
worthy of inspection by gardeners in these days of plant grow¬ 
ing for room decoration, as the best examples of culture will 
be represented. We understand the Duke of Bedford provides 
prizes for collections of “ market plants,” for wtich there will 
be spirited competition, and the arrangements are sure to be very 
effective, but of these prizes no information has been supplied to us. 
We have pleasure in making this Exhibition as widely known as 
possible, though no request for its publicity has been made to us 
by the officials, nor did we see any bills or circulars referring to it 
till Tuesday afternoon. We know from the letters of correspondents 
that the existence of the Show was not generally known early in 
the week, and that gardeners coming to London to see the “ Botanic 
Show ” on Wednesday, made arrangements for Thursday in ignor¬ 
ance of the fact that an Exhibition under the auspices of the 
Royal Horticultural Society was to be held in the Temple Gardens 
on that day. 
The Show will be opened to the public at 1 p.m. to-day 
(Thursday), the price of admission (by ticket) being 2s. 6d. until 
4 P.M., after which, and on the whole of the second day, the admis¬ 
sion will be Is. The entrance is on the Embankment, and readily 
reached either from the Temple or Blackfriars station, the former 
being slightly the nearer of the two. 
It should be added that the officials of the Royal Horticultural 
Society have been freely assisted by Mr. Newton, gardener to the 
Inner Temple Society, and every facility has been afforded in 
making the necessary arrangements. 
NOTES ON VENTILATION. 
To know how and when to ventilate can only be mastered by 
carefully observing its effects upon different plants, together with 
a thorough knowledge of the constitutions and requirements of the 
plants being treated. The quantity of air we can give a house of 
plants will also very much depend upon how we begin with them, 
and the time of year they are started into growth. A house of 
Melons, for instance, planted in January must of necessity make 
their growth with very little ventilation, and that helps to render 
their leaves thin and fragile, consequently they must be more care¬ 
fully ventilated than those planted two months later, because, to 
begin with, the latter would have more light and air, which would 
result in a robust constitution, and hence be capable of enduring 
sudden changes of temperature with impunity. 
There are very few operations more difficult to teach young 
assistants than that of ventilation, simply because they fail to realise 
its importance farther than to prevent the rise or reduce the already 
too high temperature. Very much more than that, however, is 
included in “ giving air,” for the manner in which it is done often 
determines the difference between a healthy and a sickly house of 
plants, while it is certain we should hear of and see less mildew, 
red spider, aphides, and other insect pests if the ventilators were 
always rationally worked. 
Like many other gardening operations, it is impossible to give 
detailed instructions for ventilating that can be strictly applied 
under all circumstances, hence only a few general principles can be 
pointed out, and some practical observations made upon them, 
while these will be useful in proportion as they are intelligently 
applied. Medical advisers tell us that it is not when getting hot, 
but when cooling, that the system is the most susceptible to chiUs, 
so that after getting hot we should try to reach the normal tempera¬ 
ture gradually and uniformly, hence we should avoid draughts. 
Now, experience proves that these remarks are to a large extent 
as applicable to plants as animals, so that we do not think of taking 
plants directly from hothouses to the open air, but we prepare 
them for the change by “ hardening them.” 
The fact that many plants can be grown so well without ever 
opening the ventilators proves that high temperature does not 
injure them, and the young gardener should bear this in mind when 
he has neglected to open the ventilators, and the temperature has 
run up 20° or 30° too high ; he should remember that the evils which 
follow will very much depend upon how he manages the ventilators, 
and nothing should induce him to let in a large volume of cold air, 
not even the certain knowdedge that his negligence will be dis¬ 
covered. Far more care is needed in ventilating when the tempera¬ 
ture has been allowed to rise too high than when ventilated at the 
proper time, because the air that would be comparatively warm, or 
just cold enough to be invigorating in the latter case; would be- 
chilly and often productive of baneful results in the former. The 
aim should be, under such circumstances, to reach the normal 
temperature as imperceptibly as possible by opening the ventilators- 
gradually. Not more than a quarter of an inch should be allowed' 
at first, and this should only be at the top of the house, unless the 
bottom ventilators allow the air to circulate round the hot-water- 
pipes before coming in contact with the plants. Even then the top> 
and bottom ventilators should not be open at the same time until 
after the proper temperature be reached, for that would create a 
draught, which is always injurious, more especially to over-heated 
plants ; indeed, according to our experience the bottom ventilators 
are better kept closed, except in houses where plants have finishedi 
their growth, or on very warm still days. They are certainly 
better closed in the early part of the year if we wish to be free- of 
red spider. 
But the rational use of ventilators is not to reduce but to pre¬ 
vent the rise of temperature beyond a certain point, so that on 
favourable days a little air should be admitted as soon as the tempe¬ 
rature begins rising, and it should be gradually increased as required- 
Sudden checks must be avoided in fruit and plant culture, for 
nothing is more productive of insect pest and disease. We want if 
possible to supply our houses with fresh air without creating a 
draught, and without unduly lowering the temperature, but this- 
can only be effected with the ordinary arrangements by the exer¬ 
cise of care and forethought. It may seem superfluous to say that 
more air will pass through an inch space when the wind is rough 
than would pass through a foot when it was still ; but, self-evident, 
as it is, we have often to reiterate it to our young assistants. The 
direction of the wind should always be noted, especially when it is 
rough, and if possible ventilate from the opposite side. 
There are days, however, and we have had many of them th's 
spring, when it is better to allow the temperature to rise consider¬ 
ably than to open the ventilators. There is nothing more trying- 
for forcing than hot sunshine with a high scathing wind, or alter¬ 
nate hot sunshine and sudden cold storms, and that especially after 
a period of dull weather. On such days we prefer keeping the 
fires low and the ventilators nearly closed, with plenty of moisture, 
and for tender plants shade. This we find much better than open¬ 
ing the v'entilators during such trying weather, which require -very- 
great care and constant attention, or, to say the least, an attack of 
red spider would be the result. Low span-roof houses are best 
ventilated through iron grates fixed into the wall a little above the 
ground line, and just under the hot-water pipes, and if more air be 
wanted open the doors at one or both ends as required. Plants 
very much object to a stream of air flowing directly on them ; it- 
often has the effect of drying and stunting them, and this cannot 
be avoided if top ventilators be used in low houses, hence the 
advantage of grates and opening the doors. Top ventilators, how¬ 
ever, should always be provided, as they are useful during hot still 
weather.—J. H. W. 
A CHAPTER ON CELERY. 
“ Our Celery was not good last year ” is an expression I have 
heard from scores of growers, but I am inclined to think this was more 
the fault of the grower than the Celery. Others say, “ Celery requires 
a lot of attention to bring it to perfection.” Here, again, I do not 
agree with them. It certainly needs attention, but very little sound 
cultivation is all that is required to bring Celery to the greatest 
perfection, it is often over-cultivated and sometimes neglected. 
Many understand that Celery requires a rich soil to produce 
fine heads, but this is no reason why it should be grown in little 
else than manure. I can remember the time when a layer of it was 
placed in the bottom of each trench to the depth of 9 inches or 
1 foot, a little soil was thrown in, the plants placed in this, and they 
grew freely and looked well until we began to use them, when a 
sound stick was the exception and soft pithy gro-wth the rule. 
Now not one-quarter of the manure is applied, that used is 
thoroughly mixed with the soil, and a “ pithy ” head is rare. This 
was giving it a “lot of attention” in the way of manure, but three 
parts of it was worse than superfluous. It looks well to have plenty 
of early Celery, and when folly grown by September some might 
think they were lucky, but on the contrary, as Celery is seldom 
used in any quantity until November and throughout the winter, 
and it is then it ought to be ready ; but when matured before the 
summer is over and long before it is required much of it will be 
past its best, if not useless, whereas if only one or two rows were 
grown for the earliest supply, a few more for late autumn and a 
large quantity for winter and spring, the produce would always 
