Page:Encyclopædia Britannica, Ninth Edition, v. 12.djvu/234

222 222 HORTICULTURE [PLANT HOUSES. due to the absence of rafters, which may also be dispensed with in plain roofs. Span and ridg.e-and-furrow roofs, the forms now mostly preferred, are exceedingly well adapted for the admission of light, especially when they are glazed to within a few inches of the ground. They can be made, too, to cover in any extent of area without sustain ing walls. In deed, it has been proposed to sup port such roofs to a great extent upon suspension g principles, the internal columns of support being utilized for con- S 10 15 FIG. 5. Ridcre-and-Fumnv Plant House. ducting the rain-water off the roof to underground drains or reservoirs. The lean-to is the least desirable form, since it scarcely admits of elegance of design, but it is necessarily adopted in some cases. In glazing, the greater the surface of glass, and the less space occupied by rafters and astragals as well as overlaps, the greater the admission of light. Some prefer that the sash-bars should be grooved instead of rebated, and this plan exposes less putty to the action of the weather. The simple bedding of the glass, without the use of over putty, seems to be widely approved ; but the glass may be fixed in a variety of other ways, some of which are patented. In Beard s method (a very good one) the glass is fixed between strips of felt, the covering bar being held in position by white metal nuts tightly screwed. Good results have also been obtained from the system introduced and improved by Rendle, which covers all the framework of the roof, so that the timber is not exposed to the vicissi tudes of weather. The Conservatory is often built in connexion with the mansion, so as to be entered from the drawing-room or boudoir. But when so situated it is apt to suffer from the shade of the building, and is objectionable on account of admitting damp to the drawing- room. Where circumstances will admit, it is better to place it at some distance from the house, and to form a connexion by means of a glass corridor. In order that the conservatory may be kept gay with flowers, there should be a subsidiary structure to receive the plants as they go out of bloom. The conservatory may also with great propriety be placed in the flower garden, where it may occupy an elevated terrace, and form the termination of one of the more important walks. Great variety of design is admissible in the conservatory, but it ought always to be adapted to the style of the mansion of which it is a prominent appendage. Some very pleasing examples are to be met with which have the form of a parallelogram with a lightly rounded roof ; others of appropriate character are square or nearly so, with a ridge-and-furrow roof. Whatever the form, there must be light in abundance ; and the shade both of buildings and of trees must be avoided. A southern aspect, or one varying to south-east or south-west, is preferable ; if these aspects cannot be secured, the plants selected must be adapted to the position. The central part of the house may be devoted to permanent plants ; the side tables and open spaces in the permanent beds should be reserved for the temporary plants. The kind of plants adapted for planting out in conservatories are palms, cycads, dracffinas, aralias, Inculias, camellias, &c., with fuchsias, habrothamnus, plumbago, strong-growing scarlet pelar goniums, &c., on the pillars, and tacsonias, passifloras, lapagerias, &c. , on the roof. The Greenhouse is a structure designed for the growth of such exotic plants as require to be kept during winter in a temperature considerably above the freezing-point. The best form is the span- roofed, a single span being better even than a series of spans such as form the ridge-and-furrow roof. For plant culture, houses at a comparatively low pitch are better than higher ones where the plants have to stand at a greater distance from the glass, and therefore in greater gloom. Fig. 6 represents a form of house adopted by a most successful cultivator, Mr B. S. AVilliams, of Holloway. It is 20 feet wide and 12 feet high, the length in this case being 50 feet, but of course any other convenient length could be adopted. The side walls are surmounted by short upright sashes which open out wards by ma chinery a, and the roof is pro vided with slid ing upper sashes for top ventila tion. In the centre is a two- tier stage for plants, 6 feet wide, with a pathway on each side 3 feet wide, and a side table 4 feet wide, the side tables be ing flat, and the centre stage FIG. 6. Section of Greenhouse. having the middle portion one-third of the width elevated 1 foot above the rest, so as to lift up the middle row of plants nearer the light. Span-roofed houses of this character should run north and south so as to secure an equalization of light, and should be warmed by two 4-inch hot-water pipes carried under the side tables along each side and across each end. Where it is desired to cultivate a large number of plants, it is much better to increase the number of such houses than to provide larger structures. The smaller houses are far better for cultural purposes, while the plants can lie classified, and the little details of management more conveniently attended to. Pelargoniums, cinerarias, calceolarias, cyclamens, camellias, heaths, Australian plants, roses, and other specialities might thus have to themselves either a whole house or part of a house, the conditions of which could then be more accurately fitted to the wants of the inmates. The lean-to house is in most respects inferior to the span-roofed ; one of the latter could be converted into two of the former of oppo site aspects by a divisional wall along the centre. Except where space does not permit a span-roofed building to be introduced, a lean-to is not to be recommended ; but a house of this class may often be greatly improved by adopting a half-span or hipped roof (as in fig. 9), that is, one with a short slope behind and a longer in front. Where the cultivation of large specimens of heaths, Australian plants, Indian azaleas, &c. , has to be carried on, a span-roofed house of greater height and larger dimensions may sometimes prove useful ; but space for this class of plants may generally be secured in a house of the smaller elevation, simply by lowering or removing altogether the staging erected for smaller plants, and allowing the larger ones to stand on or nearer the floor. The Plant Stove differs in no respect from the greenhouse except in having a greater extent of hot-water pipes for the purpose of securing a greater degree of heat, although, as the plants in stove houses often attain a larger size, and many of them require a tan bed to supply them with bottom heat, a somewhat greater elevation may perhaps be occasionally required in some of the houses. For the smaller plants, and for all choicer subjects, the smaller size of house already recommended for greenhouses, name ly, 20 feet wide and 12 feet high, with a side table of 4 feet on each side, a path way of 3 feet, and a central stage on two levels of 6 feet wide, will be prefer able, because more a easily managed as to r- the supply of heat and moisture. Mr Williams s plant stove (fig. 7), which FIG. 7. Section of Plant Stove. is a very good model, is of the foregoing dimensions. It has, how ever, a different arrangement from the greenhouse as to ventilation. It will be seen that along the ridge of the roof a raised portion or lantern light b, b is introduced, whicl). permits of the fixing of two continuous ventilators, one along each side, for the egress of heated and foul air, openings a, a being also provided in the side walls opposite the hot- water pipes for the admission of pure cold air.