MaskELL.—On the New Zealand Desmidier. - 255 
Closterium selengum, mihi. 
Fig. 19. 
Two of the distinguishing marks separating this plant from C. ehrenbergii 
are—the acuteness of the ends and the absence of a median inflation of the 
inner margin. The first character is constant and conspicuous. With 
regard to the second, I find that although, in its natural state, the inner 
margin forms a clear concave curve, yet in all the preserving fluids which I 
have tried an inflation becomes noticeable ; not indeed such an inflation as 
that of C. ehrenbergii, but of the nature of that shown in my figure, where 
the inner margin becomes nearly straight. Indeed, in glycerine, it is some- 
times quite straight. : 
I find also that when fronds are about to conjugate, an inflation is notice- 
able on both the outer and the inner margin, but only in the immediate 
region where the suture should be; that is, the cell-wall at that particular 
spotis bulged out all round. This, which is part of the process of conjuga- 
tion, as I am about to describe, is quite different from the wide inflation 
visible in C. ehrenbergii. 
The process of conjugation, however, as I have lately been fortunate 
enough to see up to a certain point, is the same as in C. ehrenbergii, as 
deseribed by the Rev. W. Smith, in the Annals and Mag. of Nat. Hist., 
- 1850, p. 1, and pl. i. Two fronds, each of which presents the slight 
bulging at the middle just mentioned, approach each other, and then 
become surrounded by a mucous envelope, within which they lie, longi- 
tudinally approximate, their ends almost touching, and their concave sides 
turned towards each other. Next, they proceed to undergo self-division : 
each frond separates at the middle, drawing itself out until, after the 
separation, there appear four fronds, each with one long arm and one very 
short arm, the latter terminating in a rounded short beak. Then the con- 
jugation takes place by the junction of each corresponding pair, the junc- 
tion being operated at the point where the bases of the long and short arms 
occur: and the endochrome, pouring out from each frond and joining in 
the middle, forms the zygospore, or, rather, the two zygospores, as there is 
one to each pair. Unfortunately, I cannot say precisely the nature of these 
zygospores. The specimens which I observed had been placed in a growing- 
cell, where the process just deseribed had been going on quite smoothly for 
more than twenty-four hours, from the first approach of the fronds down to 
the junction of the endochrome. At this point a sudden jar displaced the 
thin eover-glass of the cell: the conjugating fronds were crushed, and the 
process was at once brought to an untimely end. However, from what I saw, 
and from the presence in the gathering of bodies not otherwise identifiable, 
I have no doubt that the zygospores of C. selenzwm are orbicular and smooth. 
