Page:Transactions NZ Institute Volume 15.djvu/333

From the Sumner Road, Lyttelton, and very rarely from the Cust Valley.

P. jenneri, Ralfs. (R. XXXIII.) or

P. brebissonii, Meneghini. (R. XXV.)

I have great doubts which of these two occur here, or indeed whether either has come under my observation. Possibly I have mistaken Cosmarium thwaitesii for it. If P. brebissonii always occurs in colonies in mucous strata, then I have not seen it.

Very rare, in any case.

I observe that Rabenhorst and other algologists place this genus, with some of the Docidia, under Naegeli's genus Pleurotanium, so that probably Bailey's name must be given up.

T. tridentatum, mihi, var. cylindricum, var. nov.

In vol. xiii. of the Trans., p. 311, I described a plant of this species with a rectangular section. The present variety is circular in section, and of a generally thicker form. Otherwise there seems to be no difference, and the two are found together.

From the Bryndwr ditch, and also, rarely, from Hawke's Bay.

C. griffithii, Berkeley.

Fairly common. Length, from 110–160 μ.

C. venus, Kützing.

I see that Rabenhorst considers this as a separate species, though Ralfs unites it to C. dianæ. As far as I can make out, the main difference between the two is that C. venus is the smaller. However, the dimensions appear to be constant.

C. ehrenbergii, Meneghini. (R. XXVIII.)

Not uncommon.

Distinguishable, especially from C. selenæum, mihi, by its thick rounded ends and by a conspicuous median inflation of the inner margin. As to this, see below, under C. selenæum, in Part II. of this Paper.

Sp. obscura, Ralfs.

Very rare.

This plant is subject to the same disadvantage as Sp. condensata. Its distinguishing character is the spiral endochrome and this is quite destroyed by all the preserving fluids which I have tried.

Rabenhorst relegates this genus to the Palmellaceæ but as other authors include it among Desmidieæ I leave it.