INTRODUCTION. XXV 



in the soil, and that their roots are the mouths through 

 which the food is conveyed into their body. But the 

 absorption of fluid does not take place either by all the 

 surface of their roots, nor even of their fibres, but only 

 by the extremities of the latter, consisting of bundles 

 of vessels surrounded by cellular tissue in a very lax 

 spongy state, whence those extremities are called spon- 

 gioles. That it is only through the spongioles that 

 absorption to any amount takes place, is easily shown by 

 growing a plant in water and alternately preventing 

 the action of the spongioles, when languor and a cessa- 

 tion of vital action comes on, and preventing the action 

 of the general surface of the roots, leaving the spongioles 

 at liberty, when the vital energies are immediately 

 renewed. These spongioles are exceedingly delicate in 

 their organisation, and a very slight degree of violence 

 destroys them. It is scarcely possible to remove the soil 

 from the roots without injuring them in some degree 

 and if transplantation is effected violently or carelessly, 

 they are in a great measure destroyed. In proportion to 

 the size or age of a tree, is the difficulty of preserving 

 them increased ; and hence at the same time the difficulty 

 of transplantation is augmented. If, by any method, the 

 spongioles could be preserved unharmed, there would 

 be no reason whatever why the largest forest tree should 

 not be removed as easily as the young plants in a nur- 

 sery ; but their preservation in such cases is impossible, 

 and therefore the transplantation of trees of great mag- 

 nitude cannot be effected. It is because of the security 

 of the spongioles from injury when the earth is undis- 

 turbed, that plants reared in pots are transplanted with 

 so much more success than if taken immediately from 

 the soil. Hence, also, when earth is frozen into a huge 

 ball around the root of a plant, transplantation is effected 

 with the same kind of certainty. The practice of cutting 

 the roots of large trees the year previous to removing 



