24 NATURAL HISTORY SOCIETY OF DUBLIN. 



descriptions and figures permit us of judging, in its larger size, shorter 

 length in proportion to its width, and its more broadly rounded extre- 

 mities, and, if I be right in my identification of these plants, in several 

 other more positive and decisive characters, although to the accustomed 

 eye these external marks will distinguish sufficiently readily, at least 

 our Dublin forms. I do not think that P. macrococca, as Braun supposes, 

 is the same thing" as Coccochloris Brelissonii (Thwaites). According to 

 Kiitzing, in the former the cells are oblong-cylindrical, not, as in the 

 latter, sub-spherical or rotundato-elliptic. I before indicated that the 

 latter (C. Brelissonii, Thwaites) appears to me far more likely to be the 

 same plant as Trichodictyon rupestre (Kiitz.), = Cylindrocystis crassa (De 

 Bary). 



P. macrococca is not the state figured by Hicks of his lichen-gonidia; 

 for in the former the cells are oblong-cylindrical, not ovate, setting aside 

 the fact that the latter is nothing but what may be called a homomor- 

 phic representative of that which I am as yet forced to regard as a true 

 species. 



I feel satisfied that P. macrococca is not the plant so named by 

 Grunow,* of which that writer describes " the cell- contents, in certain 

 cases, as exactly like those of Zygnema cruciatum, or Desmidium;" also 

 that " a nucleus, and in each ceLL-half, a starch vesicle, were to be ob- 

 served." Moreover, we must infer from the context that his plant 

 occurred submerged in water. These characters combine in indicating 

 that it was not a Mesotsenium, but a Cylindrocystis, which Grrunow 

 must have had under observation — possibly C. Brebissoni ; but we are 

 without any figure to assist in this determination. Now, I think there 

 can be no doubt but that Palmoglcea macrococca is at all events a Meso- 

 taenium, and not a Cylindrocystis ; for those known Palmoglcea-forms 

 which actually appertain to Cylindrocystis can be best identified with 

 forms separately described under other names by Kutzing. 



Since this paper was read, I have obtained Rabenhorst's lately pub- 

 lished " Cryptogamic Flora of Saxony" (and adjacent countries). Now, 

 I have here again to remark, with every deference, that I cannot concur 

 in considering the plant figured by this author as truly P. macrococca 

 (Kiitz.). f Rabenhorst's figure certainly appears to represent the form 

 named Mesotcenium violascens by De Bary, and, if it really represented 

 the species it is called (P. macrococca), De Bary would appear to be right 

 in supposing their actual identity. But surely it will be admitted that 

 the narrow-cylindrical plant represented by Kiitzing is quite a different 

 thing from this stout, broadly elliptic form ? Yet Rabenhorst describes 

 P. violascens separately, J and considers the former (P. macrococca) equi- 

 valent to M. Braunii (De Bary) ; but if the figures given by Raben- 

 horst be compared with those of M. Braunii given by De Bary, it will 



* " Verhandlungen der k. k. zoologisch-botanischen Gesellsckaft in Wien," 1858, 

 p. 489. Grunow — "Die Desmidiaceen und Pediastreen einiger osterreickiscken Moore." 

 f " Kryptogamen-Flora von Sacksen," &c, p. 150. % Op. cit., p. 167. 



