44 PRINCIPLES OF GARDENING. [CH. I. 



themselves the moisture without which they could 

 not exist. Lastly, if seeds of plants loving a fertile 

 soil be somi along the partition, dividmg a vessel 

 into two portions, of which one portion is filled with 

 rich earth, and the other with sand, though both 

 portions are equally moist, equally loose, and equally 

 wann, all the radicles will direct their course into 

 the fertile soil. 



These facts, with many others, all demonstrating 

 that roots travel in the direction where the most 

 acceptable food is presented, overturn, beyond all con- 

 troversy, Mr. Knight's hypothesis, that the descent 

 of the root is a consequence of the laws of gravitation, 

 for these laws will not explain why roots mil grow 

 sidewise, and even upwards, if their best source of 

 nourishment is so placed as to require it — Gravita- 

 tion could only influence them to a downward direc- 

 tion, and in a fluid medium. To maintain that the 

 laws of gravitation will make the tender radicle of a 

 seed piejce the hardest soil, appears to be a self- 

 evident absurdity. 



As the radicle always advances in the direction 

 most suited to its nourishment, and in which it can 

 best exercise its functions, so does the plantlet as 

 invariably direct itself towards the surface of the soil, 

 where its leaves and stem and other superior organs 

 can alone develope themselves and perform the 

 functions bestowed upon them at their creation. 



