30 NATURAL HISTOKY SOCIETY OF DUBLIN. 



just compare it with that of De Bary's M. chlamydosporum. It will 

 be seen that our plant disagrees with that alluded to, in that it seems to 

 possess a more dense and more coarsely granular endochrome — that 

 during division the parent membrane does not seem to be cast-off as a 

 free pellicle, cap-like, from the ends of the old cells — that the zygospore is 

 ovate, not quadrate — that it becomes surrounded by a definitely bounded 

 mucous investment, and that, preliminary to the process of conjugation, 

 the parent cell-membrane is cast off (Figs. 8 to 14). On the other hand, 

 it agrees in the general form and dimensions of the cell, which in both 

 are cylindrical with rounded ends, in the form of the chlorophyll-plate, 

 and in the ultimate contraction of the contents of the zygospore within 

 the primary external coat, and the formation of a new one of an angular 

 figure closely investing the inner actual spore (Figs. 15 to 19). This 

 latter process does not take place for some time after conjugation and 

 the formation of the external coat ; hence I at first rather too hastily 

 assumed that it did not occur in our plant. However, I have met with 

 numerous specimens presenting this character, which is, perhaps, suffi- 

 cient to establish the specific identity of the plants in question. This 

 plant, then, seems 'to me to be most likely the Palmoglcea macrococca 

 (Kutz.). 



Perhaps it may not be unworthy mentioning, in case these forms 

 may occupy the attention of observers elsewhere, that the only character 

 which occasions doubt to myself as to the identity of the plant which 

 occurs here, and which I conceive to be M. Braunii (De Bary), Braun's 

 plant, referred to in his "Rejuvenescence," is that of the colour of the 

 mass. De Bary describes it as dark green, and he afterwards speaks of 

 the special definitely bounded gelatinous investments of the cells present 

 before the whole mass becomes seemingly confluent into a homogeneous 

 mucus, as. being of an intense, often dark, grey- violet colour. Now, my 

 plant is of a reddish-brownish hue in the mass, somewhat like that of 

 an infusion of tea, but deeper and richer ; the tint is deeper at the out- 

 side of the mass, and the colour is due to that of the gelatinous matter, 

 and not to the cells themselves ; but the form, structure, and appearance 

 of the latter, under the microscope, seem, so far as I can judge, entirely 

 to coincide with De Bary's figures and descriptions of his M. Braunii. 



I now proceed to describe, as best I can, a form I consider a new 

 and distinct species, though without the conjugative state, but which 

 presented to me a very remarkable condition not before noticed in this 

 genus. But, although thus apparently rare, I cannot suppose it confined 

 to the following form — in other words, I would not describe it as distinct 

 on that account. I shall defer an account of the condition alluded to to 

 the General Description of the species : — 



Mesotcenium mirificum (mihi, sp. nov.) 



Specific Characters. — Cells broadly elliptic ; chlorophyll- plate in edge 

 view very narrow, often curved. 



Habitat. — Like the former, wet rocks, but very rare. 



