Page:Transactions NZ Institute Volume 15.djvu/334

S. acutus, Meyen, var. dimorphus, Kützing. (R. XXXI.)

The cells are pointed, closely arranged in a single even row and the two outer ones are lunate.

Not common.

S. obtusus, Meyen. (R. XXXI.)

The cells are ovate or oblong and not in an even straight row.

Common.

I have had the advantage lately of perusing, in vol. x. of "Grevillea," No. 53, Sept. 1881, an article by Mr. Archer reviewing my paper on New Zealand Desmidieæ. It has been a great satisfaction to me that so acknowledged an authority does not find grave fault with the descriptions which I gave of my new species, nor, in general, with the paper itself; and Mr. Archer's remarks have gone far to clear up some points upon which I have been in doubt. I take this opportunity of referring again, in a more or less explanatory way, to some of the plants therein mentioned, as well as to some others that Mr. Archer makes no comment upon.

Previously, however, I must touch upon a point referring to the whole family. Mr. Archer agrees with me in thinking that there is great reason to believe many of the Desmidieæ to be cosmopolitan, but he goes on to remark that my "identifications of certain species may not be thoroughly correct." The same thought was certainly in my own mind when writing my paper; and in my introductory remarks I observed that "in many of the species which I have set down here as European, more especially perhaps in the genus Cosmarium, I have noticed peculiarities which do not seem to have been mentioned by authors. The discussion of these would lead me beyond the scope of this paper and perhaps the characters to which I refer would not even suffice to raise the plants even to 'varieties.'" In point of fact, three reasons prevented me from attempting to differentiate these plants from European species. First, the dearth of works of reference, for it was impossible to tell whether the minute characters noticeable were referred to or not by any author elsewhere. Secondly, a doubt whether these characters might after all only have been overlooked, or erroneously referred to, by previous observers; and an instance of this is afforded me in Mr. Archer's paper in "Grevillea," where Staurastrum avicula is stated to be really, in England, "not a smooth species, but rough," and this was a plant regarding which I expressed doubts in my paper and which