98 



CASSELL'S POPULAR GARDENING. 



practice. Hence, we have cold houses, that is, un- 

 heated; temperate houses, heated from 45° to 55° ; 

 tropical houses, heated from 66° to 75°. In modem 

 as in olden times, too, the quality as well as the 

 amount of heat becomes practically a means of 

 classification. Hence, we have dry-stoves and wet- 

 stoves — in other words, those for the vegetation of 

 the dryish table-lands of tropical countries, and 

 those for plants from the semi-saturated regions of 

 stufiy woods and steaming swamps. 



From all this we arrive at a threefold general basis 

 of classifying plant structures. The first is the 

 plants, the second the temperature, the third the 

 amoimt of vapour in the atmosphere. And it is in 

 regard to the last that the chief difference is found 

 between the general plant-stove and the Orchid- 

 house. Even in the latter, temperature is a shifting 

 ground ; for the cool Orchid-house is little, if at all, 

 warmer than many conservatories. As a rule, how- 

 ever, it is more moist, and this greater degree and 

 amount of moisture is one of the distinguishing 

 marks of such houses. 



Moisture. — Considerable diversity of opinion 

 exists as to the best means of providing this extra 

 moisture to the atmosphere of Orchid-houses, or moist- 

 stoves. Surface sprinkling of all surfaces, such as 

 walks, stages, shelves, the surface of leaves, pots and 

 basiets; the placing of evaporating-pans on hot-water 

 pipes ; the use of tanks for warming, and, occasional 

 uncovering of portions of them to allow of the escape 

 of vapour into the house ; the use of a small jet of 

 steam from the boiler, or a separate source, to charge 

 the atmosphere with vapour when wanted — are some 

 of the many methods employed for generating and 

 maintaining a moist atmosphere. One of the earliest 

 and best is that of exposing large open tanks of water 

 under the shelves or plant-stages, or under the paths, 

 almost the whole length of the house, the latter 

 being covered with strong iron gratings, of various 

 patterns, and sufficiently open to allow of the free 

 passage of aqueous vapour from the tanks into the 

 atmosphere of the house. The whole body of the 

 atmosphere of the house will then have free access 

 to the water, and will take up neither less nor more 

 than the state and temperature of the same will 

 warrant. For there is a curious twofold correla- 

 tion of air in regard to water ; that given free access 

 to the latter, the air will drink up moisture exactly 

 in the dual ratio of its dryness and its tempera- 

 ture, and hence any ■ scarcity or excess of moisture 

 in the air of plant-stoves and Orchid-houses become 

 almost alike impossible when a sufficient surface of 

 water is exposed to the air. This was early recog- 

 nised by most Orchid-growers, and hence the Orchid- 

 houses of the late Mrs. Lawrence had a central tank. 



called the Lake, with hot-water pipes passing through 

 it. Mr. Rucker, one of the earliest and most successful 

 of Orchid-growers, had a large open tank under his 

 centre stage. In another old Orchid-house known 

 to the writer, a large tank, four feet broad and three 

 deep, was carried the whole length of the house. Mr. 

 "William BuU, in his group of about twenty houses, 

 each sixty feet long, in the Ashbumham Nursery, 

 King's Eoad, Chelsea, has carried tanks along one 

 or both sides of most of them, for the storage of 

 water and the dissemination of insensible vapour. 



Of course there are other great advantages in this 

 mode of storing water, besides its being a seU-acting 

 system of charging the air with the requisite propor- 

 tion of aqueous vapour, though it is almost impos- 

 sible to exaggerate its importance in this respect. 

 One point of great and vital moment in favour of 

 such means of charging plants and the air with water 

 is often overlooked : aU the water thus distributed 

 through the air is pure. Such means of raising 

 moisture leaves all the impurities of the water be- 

 hind. This is very far from the case by the use of 

 the garden engine or syringe, as the lime and filth 

 stains on so many fine-foliage plants and Orchids 

 abundantly testify. 



Again, water thus stored naturally assumes the 

 average temperature of the house. It thus becomes 

 a mediating and moderating force during the heat 

 of bright days and the cold of frosty nights, ab- 

 sorbing heat when it is least wanted, and giving 

 it back to the air when the latter cools. A lai^e 

 body of water husbanded in this manner, and 

 freely exposed to the general atmosphere of the 

 house, becomes a powerful moderating force between 

 the evils of extremes of temperature. Water thus 

 exposed is mellowed and sufficiently genialised to be 

 used for watering and sprinkling purposes with little 

 or no additions of warmer water to it. By being 

 spread over a large surface in this way, it is also 

 clarified by the deposit of any impurities. Of 

 course there are some drawbacks in winter, as snow- 

 water and cold rains in filling the tanks may also 

 run down the temperature. But a little extra heat 

 win counteract that, and in some cases a small 

 return-pipe has been laid back through such tanks, 

 to add a gentle warmth to the water, and assist in 

 the elevation of an almost insensible vapour into 

 the atmosphere of the Orchid-house. But this must 

 be done tentatively and with care, and such water- 

 heating pipes should be so arranged as not to form 

 part of the regular circulation, and so as to be readily 

 shut off and on when required or desired. Unless on 

 a very large scale, a two-inch pipe would generally 

 suffice for the purpose. Should such pipes be large, 

 and form part of the general circulation, the chances 

 are that the house would be most densely filled with 



