REPRODUCTION OF PLANTS. 95 



mule in an ascending, and its radicle in a de- 

 scending direction. Invert it as we may, the 

 result will be the same ; but on what vital energy 

 within the plant the constancy of this fact de- 

 pends, seems yet entirely uncertain. Whether 

 it arise from the tendency of upper portions of 

 plants to seek the light, or from any other cause, 

 the reason is equally obscure, and we can hardly 

 reckon on its being ascertained by the most 

 minute investigation ; it seems to belong to that 

 class of phenomena in nature whose ultimate 

 principles are too subtle for our grasp, and 

 appear to depend on that vitality which we can 

 indeed perceive most palpably in its effects, but 

 whose cause is known only to the Creator : 

 whether modern science will be permitted to 

 approximate nearer to the truth on this and 

 some few similar subjects must remain at least 

 doubtful : at all events we are not now in posses- 

 sion of any wholly satisfactory solution of the 

 difficulty. 



" That gravity is an important agent in deter- 

 mining the difference between the directions 

 taken by the root and stem, is shewn by an 

 ingenious experiment of Mr. Knight. He placed 

 some French beans on the circumference of two 

 wheels, and so secured them that they could not 



