166 F. 0. BOWER. 



surface of the wall is for the most part left free, and not 

 covered by a film of protoplasm. 



In the former case the phenomena observed would be 

 entirely intra-protoplasmic. The process might in fact be 

 compared with what is seen when two surfaces, having a layer 

 of a semi-fluid plastic substance, such as Canada balsam, 

 between them, are suddenly separated. Both surfaces remain 

 covered with a film of the balsam, while between them run 

 strings of balsam of varying thickness, which are occasionally 

 branched, and sometimes have nodal thickenings. If the for- 

 mation of strings in plasmolysis be thus intra-protoplasmic, their 

 position would, as in the case of the balsam, be mainly deter- 

 mined by the conformation of the surface of the wall, and by 

 internal determining causes in the plastic substance itself, and 

 would not throw light on the present question of the mode of 

 connection between cell wall and protoplasm. I have repeatedly 

 examined the cell walls of plasmolysed cells, both in surface 

 views and when seen edgeways, and have not been able to 

 observe any continuous film of protoplasm covering their sur- 

 face. Having, however, learned from the experiments above 

 detailed that protoplasm may be drawn out into strings so thin 

 as to remain undefined with very high powers, the failure to 

 observe such films does not prove their absence, as they might 

 also be exceedingly thin. 



Taking the second possible explanation of the phenomena 

 into consideration, we have a strong presumption in its favour 

 from recent observations. In the first place, those of Stras- 

 burger on the deposition of microsomata on the cell wall, would 

 sut'gest that the protoplasm might be, so to speak, entangled 

 between these microsomata, and thus be continuous into and 

 held fast by the cell walls. Thus the attachment would not be 

 equally close over the whole surface of the wall, but would be 

 most strong at a number of points where the processes of pro- 

 toplasm are continued into the body of the wall. Secondly, 

 Fromman asserts that he has seen a continuous network ex- 

 tending from the protoplasm into the cell wall. Further, we 

 have evidence that where the protoplasm certainly does pene- 



