COPRINUS MICACEUS 349 



thin protoplasmic layer lining the cell-wall ; and he stated that the 

 strands show lively amoeboid movement. My own observations, 

 in the main, confirm those of de Bary. Young cystidia upon the 

 gill-sides (Fig. 157, A and B) or the gUl-edges (Fig. 157, D and E) 

 exhibit a foam structure internally, for their cell-contents are 

 divided up into a considerable number of vacuoles by thin plates of 

 protoplasm. If one focusses the protoplasm just inside the wall of 

 a cystidium, as shown in Fig. 157 at B, the limits of some of the 

 vacuoles can be clearly perceived. Where the plates of protoplasm 

 meet at the centre of each cell there is usually a clump of proto- 

 plasm which slowly changes its shape and position (Fig. 157, A, D, 

 and E). As a cystidium grows in size, the central clump of proto- 

 plasm, as de Bary thought, appears to be suspended by protoplasmic 

 bridles (Fig. 157, C). However, I believe that de Bary was m 

 error in supposing that the suspension is due to the presence of 

 bridles ; for, after watching the movements of the protoplasm for 

 a long time, I have come to the conclusion that the central proto- 

 plasmic clump is held in position, as in very young cystidia, by 

 thin plates of protoplasm which make up the walls of vacuoles. 

 The cell-content of such a cystidium as that represented in optical 

 section in Fig. 157 at C therefore appears to me to have a foam 

 structure like that of soap-suds. If this view is correct, the sup- 

 posed " bridles " do not traverse one great central vacuole, but are 

 linear aggregations of protoplasm, each one formed where three 

 protoplasmic plates meet together. The central clump of proto- 

 plasm, in the course of several minutes, moves slowly and irregu- 

 larly about a more or less central cell-position and, at the same 

 time, changes its shape. I believe that this movement is due to 

 alterations taking place in the relative volumes of the surrounding 

 vacuoles. I was unable to observe protoplasmic streaming of the kind 

 that is so well known in the bridles of the epidermal cells of Flower- 

 ing Plants. In vain did I endeavour to detect particles moving 

 along the strands of protoplasm. Several times, however, I saw 

 two strands, which together formed a V, become Y-shaped rather 

 quickly ; but this I now believe to have been due to a rather rapid 

 alteration in the relative size of the associated vacuoles. There can 

 be no doubt that some kind of protoplasmic streaming must go on 



