SiLBERIiERG: STIMULATION OF STORAGE TISSUES 



491 



a 



experiment was repeated, placing both the control and the poi- 

 soned specimens in the same dish. 



For cutting the tissues a copper tube was first used. Then a 

 silver tube was substituted, as it was thought that the copper might 

 have some effect upon the tissue with which it came in contact. 

 But on comparing results, it appeared that the copper had had no 

 effect upon the tissue. The tube, and the 

 scalpel and forceps used in handling the 

 specimens, were always placed in boiling 

 water for a few minutes before each time 

 they were used. The poisoned speci- 

 mens and the control specimens were 

 always taken from the same plant and 

 were prepared in the following way : 

 The potato, kohl-rabi, or whatever plant 

 was used, was thoroughly washed and 

 dried. Then the silver *tube was pushed 

 through the fleshy part of the plant root 

 or tuber, and the cylinder thus cut was 

 pushed out onto a piece of clean fifter- 

 paper. It was then usually cut into pieces 

 20 mm. long, — the tube was 7 mm. in 

 diameter. The part closer than 3 or 4 

 mm. to the end was never used. In the 

 cases of the roots, where there was a 



b 



longitudinal axis, the pieces were cut Figure i. a, Diagram 

 with the longitudinal axis. This was re- ^^'^^'•"g '^' '"'^""^^ '" ^^^^^^ 



^ . the cylinders of tissue were 



peated until a sufficient number of pieces ^^^^^^ j^ ^^^ ^^^t^,^ dj.l^es; 

 of each plant was cut 



Three pieces of each kind succes- 

 sively were put into a small bottle con- 

 taining the zinc sulphate solution of re- The liquid in the dish is mer- 



quired strength ; and the same number cury. 

 was put into a like bottle containing dis- 

 tilled water. This was done in order that all factors of moisture, 



^, diagram showing arrange- 

 ment for collecting COg given 

 off for relatively short periods 

 from small portions of tissue. 



etc. 



— except that of the poison — might be as nearly the same as 

 possible. After being left in the solution, or the water, for two or 

 three minutes, the pieces were taken out with forceps, rolled upon 



