Ohap. III. OF THE RADICLE OF THE BEAN. 147 



other in 8 h., within which time squares of card usually 

 act ; but after 24 h. there was slight deflection. 



An OYal bead, or rather cake, of dried shellac, 

 1 • 01 mm. in length and " 63 in breadth, caused a 

 radicle to become deflected at nearly right angles in 

 the course of only 6 h. ; but after 23 h. it had nearly 

 straightened itself. A very small quantity of dissolved 

 shellac was spread over a bit of card, and the tips of 

 9 radicles were touched laterally with it ; only two of 

 them became slightly deflected to the side opposite 

 to that bearing the speck of dried shellac, and they 

 afterwards straightened themselves. These specks 

 were removed, and both together weighed less than 

 y^th of a grain; so that a weight of rather less 

 than 5^th of a grain (0 • 32 mgs.) sufficed to excite 

 movement in two out of the nine radicles. Here 

 then we have apparently reached nearly the minimum 

 weight which will act. 



A moderately thick bristle (which on measurement 

 was found rather flattened, being 0'33 mm. in one 

 diameter, and 0"20 mm. in the other) was cut into 

 lengths of about ^th of an inch. These after being 

 touched with thick gum-water, were placed on the tip 

 of eleven radicles. Three of them were affected ; one 

 being deflected in 8 h. 15 m. to an angle of about 90° 

 from the perpendicular ; a second to the same amount 

 when looked at after 9 h. ; but after 24 h. from the 

 time of first attachment the deflection had decreased 

 to only 19^ ; the third was only slightly deflected 

 after 9 h., and the bit of bristle was then found not 

 touching the apex ; it was replaced, and after 15 

 additional hours the deflection amounted to 26° from 

 the perpendicular. The remaining eight radicles 

 were not at all acted on by the bits of bristle, so that 

 we here appear to have nearly reached the minimum 



