140 Hints for the Cidtivation 



That Orchideae cannot subsist long on dead standing trees is, I 

 think, obvious ; for the bark must become so heated and dry as 

 to absorb or destroy any moisture the plant may derive from the 

 atmosphere or contain vi^ithin itself But, again, this will by 

 no means apply to those remaining on dead fallen trees ; as v\^e 

 may suppose them to be shaded by the neighbouring trees ; and 

 I can only account for their sickly appearance by supposing 

 that the circulation of the air is not so free, and that they do 

 not imbibe so much of the moisture proceeding from the rivers 

 and low grounds. 



The atmospheric changes are very great in tropical climates ; 

 and, as I consider that Orchideae derive their main support 

 directly from the atmosphere, I think too much attention cannot 

 be paid to the various changes by which they are, in their 

 natural state, liable to be affected. One of the principal objects 

 kept in view by growers of Orchideae appears to be the keeping 

 up a regular heat in their stoves. Nothing can be more contrary 

 to nature : for, in the tropics, to a sultry day, with the thermo- 

 meter standing at from 85° to 95°, succeeds a cool night and a 

 cold morning, the thermometer falling to 60° or 55° \ effecting, 

 in twenty-four hours, a change of temperature of from 20° to 30°. 

 During the dry seasons, periods of two, three, and often extend- 

 ing to five and six months, the whole nourishment derived by 

 the Orchideae must be communicated through the agency of the 

 tree to which they are attached, or from the atmospheric 

 moisture which is the effect of the action of the sun upon the 

 dew which has fallen during the night and morning : for the 

 situations generally occupied by Orchideae preclude the pos- 

 sibility of the dew reaching them in its descent; and, slight 

 though the moisture be which is communicated through these 

 channels to Orchideae, it is nevertheless sufficient to retain the 

 vital principle in the pseudo-bulb, though not sufficient to 

 rouse it into action. The dry season, then, appears to act upon 

 Orchideae on much the same principle as our winter acts upon 

 our trees, &c. It is for them a period of rest; and the pseudo- 

 bulbs, having been well ripened, are ready, when the wet season 

 has given them a sufficient stimulus, to push forth luxuriantly 

 both leaves and flowers. 



It sometimes chances that Orchideae become detached from 

 their natural position by wind or some other natural cause; and 

 the only epiphytal Orchide^ I have seen thriving on the ground 

 are Oncidium luridum and the various catasetums. These 

 appear to do as well in mould as on trees. The other genera I 

 have found in that situation were evidently fast decreasing and 

 verging to decay. But the contact with the mould appeared to 

 have a curious effect upon Oncidium papilio, which I found in 

 abundance on the Spanish Main ; namely, that of darkening the 



