COSMARIUM. 181 



extremity ; semicells compressed-elliptic and sparsely 

 granulate, granules acute and very minute, about 8 

 showing at the margin of a semicell and 5-7 widely 

 and irregularly scattered over the surface. Side view 

 of semicell subcircular, with about 6 marginal granules. 



' o o 



Vertical view elliptic, ratio of axes about 1 : 1*7, with 

 about 9 (6-10) marginal granules. Chloroplasts axile, 

 one in each semicell, each with two pyrenoids (some- 

 times with only oner). 



Zygospore unknown. 



Length 12-13 M ; breadth 11-18 /i ; breadth of isth- 

 mus 7'5 9^u; thickness 6'o-S/n. 



IRELAND.- -Pool near Lough Glentornan, Donegal ! 

 Small Sphagnum-pool, Ballynahinch, Galway ! 



AVe have only observed this minute species twice, and 011 

 each occasion among the submerged Sphagnum of a small 

 boggy pool. We pointed out in 1902 (' Alg. 1ST. Ireland/ 

 p. 42) that the original description and figures were not very 

 accurate. The granulation is very delicate and easily over- 

 looked on the vouno-er semicells. The granules themselves 



/ O O 



are pointed, and very sparingly and irregularly scattered. 

 The structure of the chloroplasts can only be ascertained 

 with difficulty., and although many specimens possess two 

 pyrenoids in each semicell, others apparently possess only 

 one. 



C. sijntlilibomenum should be compared with C. orthostichum 

 var. pumilum, from which it is distinguished by its much 

 smaller size, its more delicate granulation, and by its fewer 

 and irregularly scattered granules of conical shape. A 

 similar type of granulation appears to occur in a Desmid 

 described by Schmidle from the Alps as Dysphinctium sparsi- 

 punctatum (vide Schmidle,, ' Beitrage alp. Alg/ 1895, p. 348, 

 t. 15, f. 1-6), only it is of a still more delicate character, and 

 frequently merely a puiictulation of the cell-wall. The 

 granules of C. synthlibomenum are of a definite conical shape, 

 and the cell-outline is quite constant in character. 



173. Cosmarium protractum (Nag.) De Bary. 

 (PL LXXXII, fig. 8 ; PL XCIV, figs. 4, 5.) 



Euastrum (Cosmarium) protractum Nag. Gatt. eiuzell. Alg. 1849, p. 119, 

 t. 7 A, f. 4. 



