Food from the Soil 151 



bladders; and the Butterwort catches its victims by 

 means of the sticky glands with which its leaves are 

 thickly covered, rolling up its edges over them and 

 undoubtedly eating them. 



The various Pitcher-plants also feed upon the large 

 number of insects drowned in their receptacles, which 

 are from two or three to as much as eighteen inches 

 deep, and always contain water. 



But, whether or no many plants are actual flesh- 

 eaters, it is certain that they all need nitrogen; and 

 other food, however abundant, will not be enough for 

 them, or enable them to grow properly, if they be 

 stinted in this respect. Their more usual way of 

 obtaining it, however, is from the soil, or from the air ; 

 but in neither case can they take the pure gas itself; 

 it must be in the form of a compound before they can 

 make any use of it. 



By way of trying whether plants could do without 

 nitrogen, other than that by which they are surrounded 

 in the air, three pots were filled with a soil of sand and 

 brick-dust, from which all animal and vegetable matter 

 had been removed. A couple of sunflower-seeds were 

 planted in each, and all three were watered with pure, 

 distilled water, containing no food whatever. 



The plants in the first pot turned out mere dwarfs, 

 as was to be expected ; those in the second were not 

 much better, though they had had a small quantity of 

 clover-ashes given them ; but those in the third were 

 almost as large as the finest specimens grown in the 

 garden, for they had been supplied with a compound 

 of nitrogen, in the form of potassium nitrate; and 

 while the two first had managed to get only about the 

 thirtieth part of a grain of nitrogen from the air, these 



