PROCESS OF VEGETABLES. 89 



diciUar direction. Mr. Knight has ascertained, Ph'il. 

 Trans, for 1806, that a strong centrifugal force apphed 

 to vep-etating seeds will considerably divert the root from 

 this direction outwards, while the stem seems to have a 

 centripetal inclination. (15) 



Tlie young root, if it grew in a soil which afforded no 

 inequality of resistance, would probably in every case be 

 perfectly straight, like the radical fibres of bulbous roots 

 in water ; but as scarcely any soil is so perfectly homo- 

 geneous, the root acquires an uneven or zigzag figure. 

 It is elongated chiefly at its extremity*, and has always, 

 at that part especially, more or less of a conical or taper- 

 ing figure. 



When the young root has made some progress, the 

 two lobes, commonly of a hemispherical figure, which 

 compose the chief bulk of the seed, swell and expand, 

 and are raised out of the ground by the ascending stem< 



(15) [In this experiment a number of seeds of the Garden 

 Bean were confined on the surface of a vertical wheel, which 

 was made to revolve rapidly by a stream of water that like- 

 wise moistened the seeds. When germination took place, the 

 radicles tended uniformly toward the circumference and the 

 plumules towards the centre. When the wheel was placed hor- 

 izontally, the radicles and plumules pursued an oblique direc- 

 tion, intermediate between that of the centrifugal and gravitating 

 forces. Mr. Knight accounts mechanically for the direction of 

 the young plant, upon the principle of gravitation, the radicle 

 being elongated by parts successively added to its apex or point, 

 the plumule by the extension of parts already formed.] 



* As may be seen by marking the fibres of Hyacinth roots \n 

 water, or the roots of Peas made to vegetate in wet cotton wooL 



