14 TKEATMKXT OF EPIPHYTAL ORCHIDS. 



and moisture are judiciously applied, and only when the plants 

 are in full vigour and in good health ; so we find that air 

 plants, although naturally subjected to a high temperature, 

 may, with proper precautions, be grown witli advantage in a 

 much lower one ; and as all plants grown in a lower tem- 

 perature than their natural one require less moisture, so Or- 

 chids, in a cool atmosphere, should be kept drier during a 

 certain period of the year ; an increase of moisture should 

 only be given with an increase of heat, and that only in the 

 growing season. It should be recollected that no plants can 

 exist for any very great length of time without rest, and tliat 

 rest is induced in a tropical climate by drought, in the same way 

 as low temperature in our own country suspends vital energy : 

 therefore Orchids must be subjected to the usual seasonable 

 clianges of rest and activity. Rest is induced by withholding 

 moisture from their roots, and partly from the air, and this state 

 of things may be considered to rejoresent their winter. Spring 

 sliould be imitated by gradually reviving vital energy by increase 

 of moisture, first to the atmosphere, and afterwards to the roots 

 or soil, accompanied by a proportionate increase of temperature : 

 this period of their growth should be very slow. Summer must 

 be represented by a greater increase of both heat and moisture ; 

 partial shade should also be resorted to to bring the energy of 

 the plant into full force. And lastly, an autumn must be cre- 

 ated to bring about maturity, by gradually reducing the quantity 

 of both heat and moisture, until the plants are again brought to 

 a fit state for repose. The first and last stages should be of but 

 short duration, and require caution, otherwise much mischief 

 may be done to the plants. 



By growing Orchids in the mean instead of maximum of heat 

 and moisture, they will not make such rapid growth ; but they will 

 become more robust and healthy, and be less liable to receive 

 injury from sudden transitions, either of heat, drought, or 

 moisture, in the atmosphere. 



The temperature of the house can only with certainty be kept 

 regular by night, particularly in summer ; therefore the fire 

 should never raise the heat of the principal house higher than 

 60°, and about five degrees less shoidd be maintained where the 

 plants are in a less excitable state : but as the days lengthen, so 

 the temperature may rise; yet it should if possible never range 

 higher than 75° by night in summer ; it will occasionally, how- 

 ever, be higher in very warm weather, and should be counteracted 

 as much as possible by evaporation and ventilation by night, 

 and by both, as well as by shading, by day. Injury is often 

 effected by a sudden rise of temperature by fire heat in winter, 

 while little or none is caused if the rise is occasioned by sun- 



