26 PLANT LIFE ON THE FARM. 



into soluble bicarbonates, and exercises a similar power 

 of solution in the case of phosphates. 



Leaves and Leaf Action. The two great factors in 

 the feeding of the plant are the roots and the leaves. 

 The soil supplies to the roots, as we have seen, water in 

 large quantities, gases, earthly and saline substances ; 

 but the air is an equally important source of nourish- 

 ment, or even more so, since there are rootless plants, 

 and plants which receive no part of their food directly 

 from the soil, while no plant can exist without air, and 

 no plant that is of direct importance to the cultivator 

 can live without light. We insert the word " direct " 

 because there is a whole group of plants which can thrive 

 in the absence of light, but these form no part of the 

 ordinary crops of a farm. Indirectly, however, as has 

 been pointed out, in considering the agency of bacteria 

 as ferments in the soil, these organisms to whose career 

 light is not essential may be of the greatest consequence 

 to cultivators ; and it is probable that the future will 

 show us much more fully how great is our indebtedness 

 to them. For our present purpose, we have to deal with 

 plants producing leaves, to point out some of the work 

 which the leaves do, and to give some indication of how 

 they do it. 



Unlike the root, which originates from within the sub- 

 stance of the plant and breaks its way out to the surface, 

 the leaf, as has been stated, is a direct production from 

 the surface of the stem or branch. It is one of the char- 

 acteristics of a root not to produce leaves ; it is one of the 

 attributes of the stem and its subdivisions to clothe 

 themselves with these appendages. 



In form, texture, size., the leaf presents infinite variety. 

 Sometimes it is a mere dry scale, sometimes a thick, 

 fleshy excrescence ; now it offers a broad, banner-like 

 surface, now it is reduced to the form and dimensions of 



