PLANT STRUCTURES. 
45 
tilation rests a great share of the superiority of modern over the 
old erections still to be occasionally met with, with ceiled roofs, 
and large brick piers between the front sashes. A greenhouse, 
to be perfect in this particular, should be so constructed as to 
allow a free and full admission on all sides, so necessary in 
summer. And it may happen, in winter, that the wind blows 
briskly from one quarter for the space of a week; if that also 
happens to be the south, or south-west, no air can be admitted 
till it ceases, unless there are ventilators on the north side. 
Some may say that when it is necessary to shut the front sashes 
it is time to close all round, but our experience speaks to the 
contrary. A proper supply of pure air is as essential to the 
health of the plants as the soil they grow in. Another subject 
here presents itself, of much consequence, yet seldom attended 
to ; we advert to draining. There is always a great quantity of 
surplus moisture falling from the roots after watering—from 
syringing—from the perspiration of the plants, and from other 
causes, in every place of the kind,—which, if not carried off, 
must stagnate, and render the atmosphere of the house impure, 
causing mildew, fogging, &c. An inattention to this we believe 
to be the fertile cause of failure in many establishments; an evil 
so easily obviated surely requires only pointing out to be remedied. 
Every house should have a drain crossing it length wise, with 
two or three trap gratings, to prevent the ingress of unpleasant 
effluvia and cold air. 
The situation of shelves, stages, &c., must depend entirely on 
the description and number of plants to be grown. And here 
we may remark, it is greatly to be wished that in the erection of 
structures of this kind, the practical gardener should be more 
frequently consulted. The assistance of an architect may be 
necessary to ensure the proper completion of the work, but it is 
the gardener alone who can know anything of the working of 
the house when finished. He, having passed a life in studying 
the subject, must be the best judge of what is desirable, and 
what should be avoided. A building may be pleasing to the 
eye, and in accordance with the finest taste, but that does not 
always ensure its efficiency to the desired end. 
We may be expected to say something of the site, but in the 
