12 



them with their 

 porous cell Avail, 

 and absorbing such 

 part of the watery 

 layer as they touch. 

 It needs little know- 

 ledge of the laws of 

 diffusion and capil- 

 lary attraction to 

 see that the fluid so 

 absorbed is made 

 good by neighbour- 

 ing water-particles, 

 and that, given ab- 

 sorption at any 

 point, an indraw 

 takes place towards 

 it. Every root-hair 

 then is a centre of 

 attraction to the 

 water constituting 

 the moisture-layer 

 of all particles of 



earth within its range. And such absorptions, multiplied 

 by millions, amply supply the almost incredible number 

 of gallons of water daily transpired as vapour from the 

 foliage of a large tree. 



13. But have these physiological facts any value in prac- 

 tical work? Much every way. They are what all successful 

 tree culture is founded on, whether the workman knows 

 and intelligently applies them, or whether he follows em- 

 pirical rules that have been taught him without explanation 

 of the reason for them. They show that compact, unaerated 

 ground, which has never been mixed up with its own bulk 

 of air by trenching to something more than the depth to 

 which average roots penetrate, is not fit to grow trees. 

 They show that the unfitness is only locally and partially 

 rectified by digging out a two or three foot hole and 

 making its earth contents as loose, aerated and open as the 



Figure 6. 



Figure 6. Absorptive tips of root-hairs, highly magnified. 



