Maskell. — On the Neiv Zealand Desrnidiese. 255 



Closterium selenceum, mihi. 



Fig. 19. 



Two of the distinguishing marks separating this plant from G. 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 (7. 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 

 spot is 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 

 described by the Kev. W. Smith, in the Annals and Mag. of Nat. Hist., 

 1850, p. 1, and pi. 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 described 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 cover-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. selenceum are orbicular and smooth. 



