RESEARCHES ON PROTOPLASMIC CONTINUITY. 309 



cut surface, and that the substance of the wall itself was quite 

 free from them. 



I proceeded to make several experiments to test the truth 

 of this conclusion. When sections of the petiole are cut in 

 water a considerable amount of latex escapes from the injured 

 surface and runs over the section, and it seemed not impossible, 

 that the latex mechanically deposited on the cut surfaces of the 

 cell walls had reduced the silver. In order to expel the latex 

 as much as possible before cutting the sections, a short piece 

 of the petiole was taken and fitted into a bored india-rubber 

 cork, which was then tightly fastened into the shorter limb of 

 a manometer tube. The manometer was filled with mercury, 

 with the exception of a short length next the cork^ which con- 

 tained water. Then, under a pressure of about 50 inches of mer- 

 cury, a current of water was rapidly driven through the petiole 

 tissue, and the latex was almost entirely expelled. Sections of 

 the petiole however, showed the same granular appearance as 

 in the first instance, thus proving that the latex had not been 

 the cause of the reduction. Indeed, direct observation of 

 sections of fresh petiole showed that little or no reduction had 

 taken place in the laticiferous cells. 



It was still possible, however, that some of the contents of 

 the other cells might have been smeared over the walls either 

 in the act of cutting or of escaping when cut. Thin sections 

 of the petiole were cut, some of which were vigorously shaken 

 with water in a test-tube. They were both treated together 

 with silver nitrate. In the shaken-up sections there was much 

 less reduction than in the others. I then resolved to try alcohol 

 material where coagulation and hardening of the protoplasm 

 would occur, and there would be a greater propability of 

 getting a clean surface. In order to make out whether the 

 action of the alcohol would interfere with the reduction of the 

 silver, sections of fresh petiole were cut in water, and then 

 treated with absolute alcohol. Having been washed with 

 water, and treated with silver nitrate in the usual manner, 

 they were examined, and it was seen that they exhibited the 

 granulation quite as well as fresh sections. Thus having 



VOL. XXIII. NEW SEK. X 



