AKCUER ON PALMOCKLCEA MACEOCOCCA (ivUI'Z.)- 13 



Moreover, as it appears to me, not only would this diversity become ap- 

 parent by even a single observation, but, so far as my own restricted 

 experience goes, would a repeated examination of examples of these 

 plants, obtained from various situations and on different occasions, tend 

 equally to establish for each of the so discriminated specific forms a 

 constancy of its own special characteristics. 



But at this point I grant that, as my collections in this genus Meso- 

 taenium, of which I have met with at least four, I believe distinct species, 

 have been all taken from the Dublin and "Wicklow mountains, my ex- 

 perience of them is confined, I regret to say, to the examples attainable 

 from only a comparatively limited area. It is therefore possible that, 

 could one see fresh specimens of the genus in question taken from very 

 distant localities, say from the different countries of Europe, that a re- 

 liance in their constancy, apparently established by Dublin specimens, 

 might perhaps be rendered less certain or even overthrown by an exa- 

 mination of foreign examples. But, indeed, so far as I can see, there 

 seems no reason to suppose such a probability. I have had an oppor- 

 tunity to examine dried specimens of not a few of the more common 

 species in the by no means distantly related family Desmidiaceoe — from 

 Germany, from Trance, from Scotland, from England, and from Ireland ; 

 and in all, the same species appear to me to possess always the same es- 

 sential specific characters, and there seems to me no reason why the 

 species of Mesotasnium, if obtained from such distant sources, should not 

 also maintain their own specialities. 



It is true that, for the reason already stated, that is, the very sim- 

 ple structure and want of any complexity of outline, and the consequent 

 paucity of readily tangible diagnostic characters, I cannot feel absolutely 

 positive that any of my Dublin plants are truly identical with those de- 

 scribed by Continental writers. I can only say that I consider it ex- 

 tremely probable that three of them are identical with as many of Pro- 

 fessor De Bary's species.* Be this, however, as it may turn out, a 

 very short examination of fresh, and, if possible, conjugated specimens, 

 would, I think, readily settle that point, and the Dublin forms at least 

 seem to me perfectly distinct from each other. But in this genus, in- 

 deed, the specimens for examination should be fresh, their distinctions 

 depending so greatly on the character of the endochrome ; so much so, 

 indeed, that the very genus would hardly be recognisable in examples 

 prepared or mounted in any way ; though, being informed of the genus, 

 it might be perhaps possible to recognise from each other, by minor 

 characters, forms with which one had been previously acquainted in the 

 fresh condition. 



Before proceeding to the subject proper of this communication, I 

 shall call to mind the characters of the genus Palmoglcea (Kiitz.) itself, 

 thus defined by Kutzing :f — " Stratum gelatinosum difforme indetermi- 

 natum, ex cellulis sparsis polygonimicis in substantia gelinca nidulan- 



Op. cit, p. 30, t. vii.. f "Species Algarum," p, 227. 



