CHEMISTRY OF MANURES 169 



box with a glass side to it. Suppose we detach one of 

 the tiny rootlets, and examine it, after splitting with a 

 razor, under a powerful microscope. It will appear like 

 Figure 2. Notice how the cells marked (a) have got 

 worn and flattened down, and how those marked (6) 

 are fresh and full. The rootlet had been pushing its 

 way among some desirable substance, which, dissolved 

 in rain water is thereupon absorbed, and such ingredients 

 as are required are passed up the central " staircase " of 

 cells which are ranged in the form of a tube from the 

 merest tip of a rootlet to the leaf vein itself. The worn 

 cells at the tip simply remain as a protection whilst the 

 rootlet pushes its way in and about the particles of soil. 

 If we were to sever the central " staircase " just spoken 

 of, the plant would either die or lead thereafter a much 

 restricted existence. Enterprising insects like the Turnip 

 Gall Weevil know this well enough, as we have seen, and 

 with generous seK-sacrifice they rehgiously avoid the 

 " winding stair." (See Plate 42.) 



We must not, however, conclude that plant feeding 

 only consists of sucking up sustenance from the soil by 

 means of the roots. This would be a great mistake. 

 The purpose for which a plant has roots is as much to 

 hold it down in the soil as it is to draw goodness there- 

 from, otherwise our cabbage and lettuce would be playing 

 skittles in the first high wind. Before a plant can success- 

 fully progress it must perform many other important 

 functions. For instance, it must breathe, for which lungs 

 are needed ; keep its blood in circulation, requiring a 

 heart ; it perspires through the skin, digests its food 

 within a stomach ; and then must ensure a place in the 

 next generation, for which in addition it must exercise 

 arts of coquetry second to none in the scheme of creation. 



Glancing back for a moment at our plant analysis, it 

 should be mentioned that the first four elements, which 

 as we said were the main constituents, come entirely from 

 the atmosphere and from the oxygen and hydrogen (as 



