Page:Transactions NZ Institute Volume 15.djvu/332

It appears to be abundant in Hawke's Bay, at least in one locality. I have not found it in Canterbury.

This plant at first sight bears great resemblance to S. dejectum, Bréb., and indeed, when seen in end view, is not to be distinguished from that plant. But, as Dr. Spencer remarks in his letter to me, the broad junction of the segments in side view renders it distinct. Ralfs observes of S. dejectum that "its segments are connected either without a band or with a very short one:" the expression of Rabenhorst is—"sinu amplo, acutangulo vel obtusangulo;" but no conclusion could be drawn from either phrase that the segments of the European plant are so closely and broadly joined as those of S. clepsydra. Indeed, Ralfs gives the breadth at constriction of S. dejectum as ¹⁄₂₇₃₂ inch, which is much smaller than that of the New Zealand plant. If S. cuspidatum, which differs from S. dejectum chiefly in the length of its connecting band, is considered a good species, the same rule might well be observed for S. clepsydra.

S. cuspidatum, Brébisson. (R. XXI.)

Not common. Two specimens from Canterbury, and a few from Hawke's Bay.

S. (Didymocladon) furcigerum, Brébisson. S. (R. XXXIII.)

The specimens which I have seen have all either five or six radiating processes in end view. Rabenhorst unites Didymocladon with Staurastrum, and says that the plant may have 3–4–6–7–8–9 rays: he omits 5. In all my specimens the rays in focus at the extreme end have the other series behind them in exact, or almost exact, correspondence with them, as shown in my figure.

For comparison with my D. stella (Trans., vol. xiii., p. 308) see below, under that species, in the second part of this paper.

Only from Hawke's Bay, where it seems to be not uncommon.

P. margaritaceum, Ehrenberg. (R. XXV. and XXXIII.)

I have specimens which, I think, can be referred to all the three varieties, α, β and γ of Ralfs. Rabenhorst unites the two first, and indeed here they all occur mingled together. As for the third, the main difference between it and the others, in England, appears to be the smaller size of its granules. None of my specimens show such large granules as are figured by Ralfs, but some are slightly constricted at the middle, while others show no constriction.

I was fortunate enough to find, on one occasion, a large quantity of this plant in full conjugation, with attached zygospores: there seems to be nothing to distinguish it from the English species.