The Nature of Orchids 



open all night too, but for fear of cats and slugs. 

 The top ventilators also should never be closed 

 during these months, day or night ; but they must 

 not be so far open as to let the damp escape freely. 

 Less than an inch suffices. On a hot summer day 

 a thoughtless gardener will open the top ventilators 

 wide, forgetting that the air will dry up in a few 

 minutes, and the plants will suffer. More fre- 

 quently, however, it is his thoughtless employer 

 who does the mischief. 



For constant damp — with ventilation — is most 

 important of all. But it must not be obtained by 

 watering the plants ; that, I think, is the commonest 

 cause of failure. Those Oncidiums mentioned, 

 clinging to naked tiles, are watered only thrice in 

 the twenty-four hours, as a rule, at midsummer. 

 This great question is treated at length in its place. 

 But I do not believe that it is possible to have too 

 much moisture in the atmosphere of the cool house. 

 The plants there come from mountains in the tropic 

 or sub-tropic zones, where rain and mist and sun- 

 shine succeed one another all the year round. 

 And on bright days the air is scarcely less damp, 

 for sunshine draws out the moisture of the sodden 

 earth. 



Another essential condition is — light. Cool 

 species, happily, are not so exacting as some in this 



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