74 ACTION OF THE RADICLE. CHAP. II. 



radicle was then allowed to grow into a narrow hole in 

 wood, 2 or 3 tenths of an inch in depth, and closed at 

 the bottom. The wood was so cut that the short space 

 of radicle between the mouth of the hole and the 

 bean could not bend laterally on three sides ; but it 

 was impossible to protect the fourth side, close to 

 the bean. Consequently, as long as the radicle con- 

 tinued to increase in length and remained straight, 

 the weighted bean would be lifted up after the tip 

 had reached the bottom of the shallow hole. Beans 

 thus arranged, surrounded by damp sand, lifted up a 

 quarter of a pound in 24 h. after the tip of the 

 radicle had entered the hole. With a greater weight 

 the radicles themselves always became bent on the one 

 unguarded side; but this probably would not have 

 occurred if they had been closely surrounded on all 

 sides by compact earth. There was, however, a 

 possible, but not probable, source of error in these 

 trials, for it was not ascertained whether the beans 

 themselves go on swelling for several days after they 

 have germinated, and after having been treated in 

 the manner in which ours had been ; 

 __^^ namely, being first left for 24 h. in 

 water, then allowed to germinate in 

 very damp air, afterwards placed over 

 Outline of piece of the hole and almost surrounded by 



fn^a^'naturS <^mp sand in a closed box. 



size) with a hole We succeeded better in ascertaining 



the U r?dicie W of iC a ^ force exerted transversely by these 



bean grew. Thick- radicles. Two were so placed as to 



narrow end -as penetrate small holes made in little 



inch, at broad end sticks, one of which was cut into the 



hole' i inch, shape here exactly copied (Fig. 55). 



The short end of the stick beyond 



the hole was purposely split, but not the opposite 



