2o THE BOOK OF ORCHIDS 



below what is considered right, no water must be 

 afforded to any of the plants, nor any damping down 

 proceeded with, before the temperature has risen to the 

 proper height, as under the circumstances the drier the 

 air of the house the less risk there is of getting the 

 plants chilled, cold and moisture combined being the chief 

 causes of spot and the commonest beginnings of disease. 



Ventilation 



Coming, as nearly all Orchids do, from hilly and 

 mountainous countries, pure air is essential to their 

 healthy development. Without it they will not thrive, 

 even in the best of houses and under the best cultural 

 skill. Ventilation must be regulated according to the 

 conditions of the external atmosphere. The general 

 rule is to give as much top and bottom ventilation as 

 possible, providing no direct draught is caused thereby. 

 In the East Indian house, with its high temperature, air 

 cannot be so freely admitted as in the intermediate and 

 cool divisions, or harm will result from the lowered 

 temperature, but with a little judgment sufficient air may 

 be admitted at all times to prevent too close an atmo- 

 sphere within. Ventilators at the apices of the houses 

 should be open for several hours each day during 

 summer, but during winter or spring, when sunshine 

 and cold winds occur contemporaneously, it is advisable 

 not to open them, sufficient air being admitted through 

 the bottom ventilators. 



As regards the Cattleya, intermediate, and cool 

 houses, plenty of air may be left on the bottom venti- 

 lators both day and night during mild weather, but of 

 course to a lesser extent during severe frosts or cold 

 easterly winds. When top air is given, discretion must 

 be used at all times. My practice is to afford only just 



