POT-PLANTS IN ROOMS 15 



dry air surrounding them, and as this rush would proceed at 

 such a rate that the supply provided by the roots could not 

 keep pace with it, their collapse would be inevitable. More- 

 over, another thing would happen — intense cold, the invari- 

 able result of the speedy conversion of a liquid into a 

 vapour. That is why a draught is so deadly. In the 

 process of sap-making by the leaves, water is produced and 

 escapes in the form of vapour through the stomata. When 

 this takes place at the normal rate, it merely keeps the leaves 

 cool ; but if it becomes very rapid, as happens when the 

 water produced is instantly carried away by a current of air 

 directed on some particular spot, the temperature there is 

 lowered excessively, and congestion is the result, the organs 

 being rendered incapable of performing their functions. A 

 moist atmosphere is therefore necessary for healthy growth, 

 and though the amount of moisture varies for different 

 species — it need not, for example, be anything like so great 

 for geraniums as for hydrangeas or ferns — the more there is, 

 as a rule, the more luxuriant the growth. In greenhouses it 

 often happens that the spores of ferns alight and germinate 

 on the damp walls close to the pipes, on which, when they 

 are heated, water is sprayed occasionally, and in this steamy 

 atmosphere the plants grow in a remarkable way. But in a 

 room the air is always comparatively dry — very much drier 

 than it is outside in the country, where moisture is always 

 exuding from the vegetation around as well as from the 

 ground. This unfavourable condition cannot be greatly 

 altered. All that can be done is to keep plants as far away 

 as possible from all fires and lamps. 



The natural position for them is near a w^indow. In 

 some respects it is the best position, for there they get more 

 light than anywhere else. It is true that certain species, 

 such as aspidistras and ferns, will live without direct sun- 

 shine ; but even for them a moderate amount is beneficial, 

 and for some others it is essential if they are to remain long 

 in good condition. Those that have coloured foliage — 

 coleus, for instance — will not acquire their colour without 

 sunshine, and, if they have previously acquired it they will 



