DARK-GROUND ILLUMINATION 351 



Myxomycetes in the " amoeba condition " were also examined, 

 and generally showed the protoplasm filled with moving 

 particles. 



In Vaucheria, Cladophora, (Edogonium, and Stigeoclonium, the 

 chloroplasts generally prevent the clear observation of the 

 cytoplasm, so that these are not good objects for study. 



The leaf edge of Elodea canadensis 1 makes quite an instruc- 

 tive object. The leaf edge is only one cell thick, and the cell 

 walls are very clear. The protoplast usually lines the cell wall, 

 while the chloroplasts of these edge cells are comparatively few 

 in number and relatively inconspicuous under this illumination. 

 " Sap particles " are nearly always present in the cell sap. The 

 protoplasm is seen to contain very numerous small particles, 

 which exhibit the usual Brownian movement. After a time, 

 circulation of the protoplasm usually occurs, and the particles 

 can be clearly seen, as they are carried on by the stream, still 

 executing their Brownian oscillations. The sap particles are 

 usually unaffected by this circulation. 



Gaidukov 2 states that towards the cell wall and the vacuole 

 the hydrosol is covered by a layer of gel — " hydrogelschict " — 

 which is produced by the contact of the hydrosol with the 

 electrolytes of the cell sap. These electrolytes coagulate the 

 hydrosol and protect the inner portion of the complex from 

 further reaction with the solution — the reversible portion from 

 forming a colloid solution with the water, and the irreversible 

 portion from coagulation. There is, of course, considerable 

 reason for identifying this layer with the plasmahaut ; but there 

 is here room for a great deal of work. 



In other cases of cells examined the protoplasm presents 

 another appearance. No discrete particles can be made out in 

 the protoplasm and no motion can be detected. In some cases 

 the protoplasm has a somewhat mottled appearance, recalling 

 perhaps the network-like structure as postulated by Butschli 

 and other observers. 



On the death of a cell which shows a structure with moving 

 particles, a complete cessation of the movement in the proto- 

 plasm is brought about. This is also naturally the case when 

 fixing agents are allowed to act on the living cell. The proto- 

 plasm then appears as a mass of overlapping diffraction images — 



1 S. R. Price, I.e. 



2 Gaidukov, Beriehte, I.e. p. 587; Dunkelfeld., etc., p. 62. 



