TREATMENT OF EPIPHYTAL ORCHIDS. 15 



heat : care should therefore be taken to guard against a rise of 

 temperature by fire heat, particularly in midwinter ; rather suffer 

 a depression of a few degrees of heat in very severe weather 

 than use over-strong fires, which will over dry the atmosphere, 

 and, on tlie other hand, create too much moisture if water is 

 supplied. Moisture, however, is by no means injurious to Or- 

 chids, provided they can part with it freely, but they are im- 

 patient of stagnant damp. 



When in a dormant state, they should receive no more 

 moisture than is sufficient to prevent their leaves from shrivelling : 

 hence many of the more tender kinds do much better on blocks 

 of wood suspended from the roof, where they can part with 

 the superabundant moisture freely, than in pots. Nature herself 

 indeed sets us an example to follow in regard to moisture, for 

 we find, where the atmosphere is saturated with moisture (and 

 a truly moist atmosphei'e cannot exist without a corresponding 

 amount of heat), that the Orchids climb the loftiest trees; but 

 as the climate becomes drier, so they descend, until at last they 

 are to be found growing upon the surface of the ground or upon 

 rocks in shady places. 



Epiphytal Orchids may be divided into three classes, so far 

 as situation is concerned, viz., those which grow on the bare 

 branches of trees, and that require a very moist and warm atmos- 

 phere ; those which require a light fibry material to cover their 

 roots, and a cooler and drier atmosphere ; and those that like 

 a cool atmosphere, and require a rich vegetable mould, re- 

 tentive of moisture, to grow in. The first, like the old air plant 

 (Aerides odoratum), have true aerial roots, and are principally 

 from the hot damp parts of the East ; the second kinds come 

 from the milder tracts, particularly of the AVestern hemi- 

 sphere ; while the third are those from an atmosphere cool and 

 dry, and which seek refuge on the ground. 



3. Soil, Sfc. 



More diflPerence of opinion exists upon this point than upon 

 any other item of their culture, and it is certainly one deserving 

 of attention ; for although it may be of little or no importance 

 to an air plant whether it is grown in rich or poor soil, so far as 

 nutriment is concerned, still it is necessary to know whether the 

 soil, or whatever its roots may be surrounded by (some use 

 nothing but broken potsherds in very small pieces), is retentive 

 or not of moisture, and whether it parts freely with the same to 

 the surrounding atmosphere when required. The best material 

 is that which is not retentive of moisture, nor liable to become 

 stagnant, or what is termed sour, and that which, under the in- 



