POT-PLANTS IN ROOMS 



13 



chlorophyll, and are converted into the sap. Certain 

 atmospheric conditions are therefore essential for healthy 

 development — a sufficiency of carbonic acid gas in the air 

 (and about this there need never be any doubt) ; moisture ; 

 no interference with the functions of the stomata ; sunlight; 

 and, of course, a suitable temperature. 



Fig. 5. — Portion of Epidermis of Leaf (highly magnified), showing 

 two stomata open and one closed. 



In a room, especially when it is situated in a large town, 

 it is not easy to satisfy these conditions perfectly ; but if the 

 plants are to remain healthy, every effort should be made 

 to do so. Dust and dirt are most injurious. They settle 

 on the leaves and, if allowed to remain, block the stomata, 

 and so prevent the entrance of the necessary carbonic acid, 

 with the result that the leaves turn yellow and wither. 

 Cleanliness is therefore essential. It is a good plan to take 

 advantage of a shower of rain and to stand the plants out 



