UPWAKD GROWTH OF THE HEAD, AND pt. ir. 



head and to OTavitv. Among tliG Humber are Diitrochet, Kniglit, 



the roots & J o ' o ' 



Experi- ^^^^ Humphry Davy, men for capacity and clear- 



proof! ^^ss intellect matchless among physiologists. I will 

 therefore go at length into two experiments of Dutro- 

 chet and Knight, the conclusions drawn from which in 

 favour of gravity have been enforced by Sir Humphry 

 Davy. Dutrochet found that if beans, in a state of 

 germination, were planted in holes through the bottom 

 of a box filled with earth, the stems grew upward 

 from the light into the earth, and the roots downward 

 towards the light into the air ; and the plants perished 

 when they ceased to derive nutriment from their 

 seeds. 



Early in March 1844, I made experiments similar 

 to those of Dutrochet, with results which, if at first 

 they resembled, finally differed very widely from, those 

 elicited by this eminent and most acute physiologist. 

 And in considering these results, I think I shall be 

 able to explain why the beans in Dutrochet's experi- 

 ment died. I placed various seeds on the surface of 

 large flower-pots full of earth, turned them over on 

 wire-work, and hung the inverted pots from the wood- 

 work at the upper part of my window, so as to have 

 the lower sides of the seeds exposed to light and air 

 from below, and their upper sides in contact with the 

 moist earth above them. The immediate results 

 showed a most remarkable determination of the first 

 or tap-roots downward, and of the gemmules or stems 

 upward. In all the experiments the first or tap-roots 



