Chap. II. 



ACTION OF THE RADICLE. 



7fi 



Fig. 56. 



end. As the wood was highly elastic, the split oi 

 fissure closed immediately after being made. After 

 six days the stick and bean were dug out of the damp 

 sand, and the radicle was found to be much enlarged 

 above and beneath the hole. The fissure, which was 

 at first quite closed, was now open to a width of 

 4 mm. ; as soon as the radicle was extracted, it imn..e- 

 diately closed to a width of 2 mm. The stick was 

 then suspended horizontally by 

 a fine wire passing through the 

 hole lately filled by the radicle, 

 and a little saucer was sus- 

 pended beneath to receive the 

 weights ; and it required 8 lbs. 

 8 ozs. to open the fissure to the 

 width of 4 mm. — that is, the 

 width before the root was ex- 

 tracted. But the part of the 

 radicle (only •! of an inch in 

 length) which was embedded in 

 the hole, probably exerted a 

 greater transverse strain even 

 than 8 lbs. 8 ozs., for it had split 

 the solid wood for a length of 

 rather more than a quarter of 

 an inch (exactly '275 inch), and 

 this fissure is shown in Pig. 55. 

 A second stick was tried in the 

 same manner with almost ex- 

 actly the same result. 



We then followed a better 

 plan. Holes were bored near 

 the narrow end of two wooden clips or pincers (Fig. 56), 

 kept closed by brass spiral springs. Two radicles in damp 

 sand were allowed to grow through these holes. The 



Wooden pincers, kept closed by 

 a spii-al brass spring, witli a 

 hole ("14 inch in diameter 

 and 6 inch in depth) bored 

 through the narrow closed 

 part, through which a radicle 

 of a bean was allowed to 

 grow. Temp. 50°-60° F. 



