Page:Transactions NZ Institute Volume 15.djvu/340

Staurastrum avicula, Brébisson.

Mr. Archer thinks that our plant may be a distinct form and says that Ralfs' figure of the English species is incorrect. I am willing to accept this, but as I have not seen any specimens since writing my former paper I am not prepared to suggest any new name.

All these minute forms of Staurastrum are difficult of identification and it would be easy to multiply species upon the slight differences occurring so frequently.

Didymocladon stella, mihi.

This plant must, I suppose, be relegated to the genus Staurastrum, as Pritchard, Rabenhorst and succeeding writers do not admit Ralfs' genus.

As to its specific status, I am in some doubt. After carefully comparing it with specimens of S. furcigerum, both from Hawke's Bay and from England, and allowing for Rabenhorst's statement that S. furcigerum may have from three to nine rays in end view, I cannot regard my S. (Didymocladon) stella as identical with that plant. In all my specimens of S. furcigerum, as remarked in the first part of this paper, whether there are five or six rays, those rays which are behind the terminal ones, and which are at first sight out of focus, are always in almost, if not quite, direct correspondence of direction with the terminal rays. I cannot see how in any case the peculiar multi-radiate appearance of S. stella can be produced by the English plant.

I find, however, in the "Midland Naturalist," a figure (vol. iv., pl. v.) of Staurastrum arctiscon, Ehrenberg, a plant mentioned by Rabenhorst as American, under the name Xanthidium arctiscon, and seemingly found lately in Wales. This plant, in end view, has six terminal rays, and eight others behind them, almost in corresponding directions. Whether, in some cases, it may show the twenty-eight divaricating rays of my S. stella I cannot say: if so, my plant will have to be abandoned as a distinct species.

S. pseudo-furcigerum, Reinsch, though its side view approaches best to that of S. stella, differs altogether in end view, being then more like S. eustephanum in general outline.

I find that Mr. Archer would refer our plant rather to Staurasirum sexangulare, Bulnheim, which I do not know.

Docidium baculum, Ehrenberg.

I expressed in my former paper doubts as to the existence of this plant here, and after comparison with English specimens I have come to the conclusion that it is not found here, or at least that it has not come under my notice. Its distinctive character is the possession of a solitary, prominent inflation at the base of each segment. All my New Zealand specimens show at least more than one inflation.