POT-PLANTS IN ROOMS 



3 



form. It cannot absorb solid matter. It has nothing corre- 

 sponding to the mouth and channels by which food is 

 conveyed to the digestive apparatus in an animal, there to 

 be prepared for distribution throughout the system. The 

 food materials must be dissolved in water, so that they can 

 be absorbed by the tips of the roots, from which they pass 

 into the various cells through the cell walls until they reach 



Fig. I. — Plant (left) recently moved from larger pot ; another (right) 

 lifted from the ground ; and a third (centre) which has been grown 



in the same pot for some time. 



the leaves. There, under the influence of light, and with 

 the addition of carbonic acid obtained from the air, they are 

 transformed into sap, which is real plant food, the material 

 of growth. 



Water is therefore essential, but the amount varies with 

 the species and with the season. Some species — aquatics 

 and subaquatics — can live in water ; others, the majority, 

 are killed if there is too much. Their roots cannot grow or 

 continue in a healthy condition without air, and if the soil 

 is sodden the interstices between its particles are filled with 



