125 



vvlietlier composed of wood, cordage, or any oilier material, 

 are of little avail in giving stability. To a body rather defi- 

 cient in proper strength, a rich and favourable soil may, 

 after some years, give an augmentation of roots and lateral 

 branches, and, in the end, a certain accession of strength to 

 the body itself. But he, who would transplant witii judg- 

 ment, should consider a vigorous stem as a sine qua non in 

 the beginning ; as success otherwise must depend on acci- 

 dents which he cannot control, and on advantages which he 

 may not procure, at an after period. 



Thirdly: Numerousness of Roots and Fibres. Roots 

 are also accounted among the conservative organs. The 

 body of the roots of trees, says Malpighi, may be regarded as 

 a production and elongation of the trunk beneath the soil, 

 and is constructed of the same textures, disposed in the same 

 manner.* Roots, like the stem, are augmented in their 

 width by the addition of an annual layer, and in their length 

 by the addition of an annual shoot, bursting from the termi- 

 nating fibre ; but they are elongated merely by the extremi- 

 ty. This is the general opinion of phytologists. It has, 

 however, of late been called in question, and great ability has 

 been displayed in making it appear, that the root is not elon- 

 gated by the extremity, any more than the stem ; or, if it be 

 so, that the rule has numerous exceptions.! 



As trees have no organs analogous to the mouths of ani- 

 mals, they are enabled to take up the nourishment, which is 

 necessary for their support, only by absorption and inhala- 

 tion, as the chyle is taken into animal lacteals, or air into 

 the lungs. This, in the language of phytologists, is termed 

 introsusception ; and the former mode, of course, applies to 

 the introsusception of non-elastic fluids, and the latter to that 



* Anat. Plantar, p. 145. 



t See Thompson's Annals of Philos. No. LXXVI. 



