490 Silberberg: Stimulation of storage tissues 



from a normal solution, prepared as follows : The zinc sulphate 

 used was Merck's "highest purity reagent." For lOO c.c. of a 

 normal solution, 14.3786 gm. of ZnSo^ would be theoretically re- 

 quired (allowing jHjD for water of crystallization). 14.5 1923 gm. 

 were weighed out, this differing from the required by o. 14063 gm. 

 14.3786 ; 100 :: 0,14063 :x. X= 0.978 c.c. of water. There- 

 fore, 100.978 c.c. of water added to 14.51923 gm. of zinc sulphate 

 makes a normal solution. The water w^as the distilled water used 

 in the laboratory. This was used also for washing all apparatus. 



The apparatus used, and the results obtained in regard to the 

 first part of the work, that is, the effect upon the periderm and 

 callus formation, will first be described. 



The glass dishes into which the specimens were to be placed, 

 after being washed in distilled water, were put in the steam steril- 

 izer, and heated at boiling point for not less than thirty minutes. 

 The first experiments were made in an atmosphere dried by having 

 a solution of potassium hydrate present in a small open dish. But 

 the specimens dried out too much and were unsatisfactory for ex- 

 amination. Thereafter the experiments w^ere conducted in a satu- 

 rated atmosphere, the dishes being prepared in the following manner. 



r 



All glassware was washed as stated above before using. The 

 bottom of a glass dish was covered about a half or three quarters 

 of an inch deep with very moist sphagnum. Then a side of a 



L 



— J- + 



Petri plate which fitted closely into the glass dish was placed on the 

 sphagnum. Then another glass dish slightly larger than the first 

 was placed over it, forming a closely fitting cover. After heating 

 in the steam sterilizer as aforesaid and cooling, the cover was 

 lifted as httle as possible at the side, and the specimens placed in 

 an upright position on the Petri plate (see figure i, a). The covers 

 of the dishes were never taken completely off during the experi- 

 ments. They were always plainly labeled with the strength of the 

 solution into which the specimens had been dipped, and the date 

 the experiment was started, so no errors could arise through con- 

 fusing the dishes — for example, *'N/i2 ZnSO^Jan. 23/09." The 

 dishes for the control and the poisoned specimens were always 



* 



prepared at the same time and in exactly the same manner. In 

 some cases where it was thought possible that a variation in results 

 was due to a difference in the atmosphere in the two dishes, the 



