TREATMENT OF EPIPHYTAL ORCHIDS. 11 



east and south-west. It should be span-roofed, but not over 

 wide, 14 feet high in the centre, and forming an angle not 

 exceeding 30^, but as near as possible that pitch ; there should 

 be no upright sashes on either sides, but it should have glazed 

 ends. The interior should be fitted up with slate stages and 

 shelves, those in the centre having a heated chamber underneath, 

 closed in, but with ventilators to allow the heat to escape into the 

 house when required. 



In heating nothing is better than hot water in 4-inch pipes, 

 which should enter at the end and run round the house in a 

 double row. The centre chamber should be heated by one flow 

 and return pipe only. Open gutters in the house, or inside the 

 chamber, are objectionable on account of their being incapable 

 of producing heat wdthout moisture, the latter being in general 

 too plentifully supplied ; for the quantity required of this as well 

 as of heat must at all times depend upon the state of the 

 external atmosphere. 



Conical boilers are in general most efficient, when properly 

 set; but much of their value, like that of all other kinds of 

 boilers, depends upon their not requiring so much attendance as 

 others. All Orchid-houses should have two boilers fitted to the 

 pipes, in order that, if any accident happens to the one, the 

 other may be in readiness to be used, or both together in severe 

 frosty weather. 



With regard to ventilation too much caution cannot be 

 observed, for in no case should direct currents of cold air be 

 allowed to enter the house : therefore the best mode of ventila- 

 tion is at or near the top through the upper lights, which may 

 be made to run down or push outwards at their lowest end, and 

 thus allow the over-heated air to escape. The supply of fresh 

 air required is but small, and may be admitted by small aper- 

 tures (furnished with ventilators) in the front and back walls as 

 near the ground as possible and below the hot-water pipes, so 

 that the fresh air may be warmed in passing among and over the 

 hot pipes. 



Moisture must be obtained by occasionally pouring water over 

 the shelves, hot-water pipes, and from small earthen evaporating- 

 pans placed over the pipes at their hottest ends. 



Shading will be found to be indispensable in bright sunshine ; 

 the necessity for this will be more apparent when it is remem- 

 bered that in all hot and damp climates the sun's rays are greatly 

 obstructed by the amount of vapour which floats in the air. 

 Shading will also be found of great service when the external 

 atmosphere is very hot and dry ; it prevents internal evaporation 

 from going on too quickly, and keeps the foliage of a brighter 

 green. If Orchids are much exposed to sunshine in summer 



