Page:Transactions NZ Institute Volume 15.djvu/345

visible in any case, beyond, that is, the folds due to the bursting of the cell-wall, which were easily recognizable. Consequently, I could only infer that the fronds had undergone self-division previous to conjugation; and on this supposition those in which the inequality was but slight would have simply missed conjugation and were growing in the ordinary way. This being the case, if I am right, it results that each pair of segments in C. acerosum produces a zygospore, and therefore each whole frond produces two zygospores; but the process differs from that of C. selenæum and C. ehrenbergii in this, that the fronds do not shut themselves up in pairs in mucus, but are all enveloped in the same envelope.

Certainly, I cannot say that I saw any fronds dividing, for the process had already begun, and was in full swing when first seen. But I am unable to account in any other way for the curious inequality of the arms.

As C. acerosum has only a suture at the middle, and no secondary sutures, the bursting of the cell-wall anywhere but at the middle cannot be explained as in C. intermedium. Penium margaritaceum and other plants also open unequally, but they too have secondary sutures.

Closterium lineatum, Ehrenberg.

This is another of the plants observed conjugating. There is nothing to distinguish it from the English species.

Closterium dianæ, Ehrenberg.

Also observed conjugating.

I add a figure (20) of Scenedesmus quadricauda, to show the three bristles sometimes observable.

Also two figures, 21 and 22, as specimens of the curious monstrosities of growth often seen amongst Desmidieæ, a family generally of such remarkable symmetry of form. Fig. 21 is Tetrachastrum (Holocystis) incisum; fig. 22 is Docidium clavatum.

An asterisk in this list marks the species described by me as new in the foregoing and my previous paper (vol. xiii., 1880, p. 297); a dagger marks those described as new by Dr. Spencer in his paper (vol. xiv., pp. 295, 296); and a double dagger those reported by Dr. Spencer in the same paper, but not new.

[Note.—I include also Docidium (Pleurotænium) ovatum, of which I find the following notice in one of Professor Nordstedt's papers—"Hæc species quoque in Brasiliâ et Novâ Zealandiâ lecta est;" but I do not know the plant.]