Page:Transactions NZ Institute Volume 15.djvu/331

At first sight this plant might be taken, in side view, for S. spinosum, or in end view for S. monticulosum, Brébisson. But it differs from the former in having its outer edges less turgid than the inner and in its processes not being on the same plane; from the latter in the more cylindrical lateral processes and their forked tips. The nearest resemblance to it is, I think, S. (Desmidium) eustephanum, Ehrenberg, an American plant, referred to by Ralfs, p. 215, without figure, and described and figured in Pritchard's Infus., p. 743 and pl. ii., fig. 3. The differences are that in the New Zealand plant the sides, in end view, are emarginate and not rectilinear as in the American variety, and the lateral processes project beyond the sides, whereas in Pritchard's figure they are very small and do not reach the sides. In S. senarium, Ehrenberg (also American), similar processes project, but there is also a second series of six others, shorter and in almost corresponding directions, behind the first. In the "Midland Naturalist," vol. iv., pl. v., Mr. A. W. Wills figures S. pseudofurcigerum, Reinsch, not unlike our plant in end view, but it is covered with minute spines on the processes as well as on the frond, and the side view is also different.

On the whole, I take this plant to be intermediate between S. eustephanum and S. senarium.

S. clepsydra, Spencer (in lit. cum specim.), sp. nov. S.

Frond somewhat large, smooth. Segments in side view broader than long, widening rapidly from the constriction which is not deep. The external edges are either straight or oftener slightly concave: lateral edges convex. Ultimate angles ending in a fine awn or mucro. In consequence of the shallow constriction the segments are closely united at the base, the junction is broad, and there is no isthmus or band whatever. The apex of the third angle with its awn is usually visible beyond the external edge of each segment.

Frond in end view triangular; the sides equal, slightly concave: somewhat mammillate at the angles which are terminated by the awns. The concavity of the sides is not always conspicuous.

Frond quite free from puncta.

I have seen no zygospores attached to fronds, but in every gathering there are a number of bodies which may not improbably belong to this plant. They resemble generally those of S. dejectum, but have fewer spines. I have been able to compare them not only with Ralfs' figures of S. dejectum, but also with zygospores of that species in my English gatherings.

Length of frond in side view 31–40 μ; breadth at external edge of segments (exclusive of awns) 30–35 μ; breadth at constriction 15–17 μ; side of triangle in end view 30–35 μ; length of awn 5 μ.