174 PROCESS OF NUTRITION. CHAP. III. 



most vigorous at the surface because they have there 

 the easiest access to the oxygene of the atmosphere, 

 or to the extract which it may form. It was ob- 

 served also by the same phytologist that perpen- 

 dicular roots do not thrive so well, other circum- 

 stances being the same, in a stiff and wet soil as in a 

 friable and dry soil ; while plants with slender and 

 divided roots thrive equally well in both : but this 

 is no doubt owing to the obstacles that present 

 themselves to the passage of the oxygene in the for- 

 mer case, on account of the greater depth and 

 smaller surface of the root. It was further observed, 

 that roots which penetrate into dung or into pipes 

 conducting water divide into immense numbers of 

 fibres, and form what is called the fox-tail root ; but 

 it is because they cannot continue to vegetate, ex- 

 cept by increasing their points of contact, with the 

 small quantity of oxygene found in such mediums. 

 Lastly, it was observed that plants whose roots are 

 suddenly overflowed with water remaining after- 

 wards stagnant, suffer sooner than if the accident 

 had happened by means of a continued current. It 

 is because in the former case the oxygene contained 

 in the water is soon exhausted, while in the latter 

 it is not exhausted at all. 



And hence also we may accounf for the pheno- 

 menon exhibited by plants vegetating in distilled 

 water under a receiver filled with atmospheric air, 

 which having no proper soil to supply the root with 

 nourishment, effect the developement of their parts 



