CHEMICAL FARMING 225 



As the plants grow they absorb considerable water, 

 if in a tank six inches in depth at the beginning, 

 dropping down to two inches at which level it should 

 be maintained, not allowing the tanks to be flooded, 

 either by rain or artificially. For this reason it is best 

 to have a drainage pipe that can be turned down (an 

 elbow at two inch level, with a nipple, answers ad- 

 mirably) after the plants are well started. This ar- 

 rangement of an air space of about four inches be- 

 tween the water and wire netting is beneficial to the 

 roots as they are growing in a moist dark air cham- 

 ber, reaching for water, and a sudden flooding is 

 definitely detrimental. Being covered by a layer of 

 excelsior, consequently dark, the solution breeds 

 neither algae nor mosquitoes, but remains fresh and 

 clear through the growing period. 



In the case of soil-grown plants, they must reach 

 out their roots to gather their nutritive elements, 

 often to considerable distances; the failure to find 

 this or that, to it, necessary element is the cause of 

 poor crops, or under-color or development of flowers 

 or plants. In tanks, containing all their needed ele- 

 ments, their roots are shorter, more numerous, allow- 

 ing much closer planting, a decided economy of 

 space; even plants having in soil a long tap root 

 change their habit and form a close out-spreading 

 mass. The limit of their nearness together seems to 



