223 



The author of the above named article holds the latter view, 

 and claims to have answered the two principal objections which 

 the believers in the osmotic theory raise against it. These ob- 

 jections are, first, that no protoplasm has ev^er been discovered on 

 the surface of the cell wall. Second, that the existence of pores 

 of such character as to allow such an exudation has never yet 

 been satisfactorily proven. 



The latter objection, he claims, can no longer be urged against 

 the forms he studied, the genus Navicular chiefly the group Pin- 

 nularia. He gives a long and concise description of the anatomy 

 of several forms, in which winding canals along the raphe are of 

 such shape and size as to render it possible for the protoplasm to 

 be pressed out to the surface, and at the same time prevented 

 from escaping by a compHcated arrangement of these tubes, so 

 that if a quantity of protoplasm is pressed out at the central open- 

 ^*"gs, a corresponding amount is taken up by suction at the ends 

 of the cell, or vice versa, according to the action of the forces 

 within which press the protoplasm outward. In this way a ro- 

 tary motion of protoplasm may be kept up on the surface of the 

 cell so that a small portion of the same is exposed to external 

 contact 



He does not claim to demonstrate ** ad oculos *' the actual 

 appearance of plasma on this surface in any other way than has 

 already been done by previous investigators, that is, by the glid- 

 ing along of foreign bodies on these parts of the cell. But he 

 does claim to have proven the existence of the pores, and also 

 that certain conditions exist inside the cell wall which must have 

 for a result the forcing out of a small portion of the protoplasma 

 through these channels. This is shown by the action of various 

 reagents on the living protoplasm within the wall, by which the 



r 



presence of a certain amount of turgor is proven. He states that 

 diis question of turgor has never before been directly answered 

 5n botanical literature. By the use of a ten per cent, solution of 

 potassium nitrate a complete cessation of motion was produced, 

 but no plasmolysis; on the application of fifteen per cent, the 

 first indications of plasmolyses occurred, which increased with the 

 mcreasin^ strenirth of the reatient. 



. ... ^. ....v -v-.*j^ 



From these experiments the author concludes, first, that the 



