330 THE JOURNAL OF BOTANY 



has been monotypic, D. rejiiformis Hieron.''' having been originally 

 described from the Sudeten Mountains in Silesia, and since found 

 by Virieux f in France. Lagerheim also records it from near 

 Berlin. 



D. hritannica is distinguished from D. reniformis by the 

 smaller size of the cells, their different external form, the absence 

 of dorsal tubercles, the lamellose character of the cell-wall, 

 and the dorsal attachment of the seta. In D. reniformis the 

 cells, when viewed from above, are reniform in shape, the seta 

 arising from the base of the cell and passing upwards through 

 the indentation. In D. hritannica, on the other hand, there 

 is no lateral groove, and the seta is dorsal or subdorsal in its 

 insertion. 



The chloroplast was massive, and its limitations could not be 

 satisfactorily determined from the specimens, all of which were 

 fixed in formalin. No pyrenoid was present, but small grains of 

 starch could be detected. All the specimens observed were free 

 in a sediment obtained by squeezing submerged Sjjhagnum, but 

 there is every reason to suppose that in the living condition they 

 would be attached to the Sphagmcm leaves. 



D. reniformis was obtained by Hieronymus attached to 

 Sphagmcm leaves, and by Virieux " sur les feuilles des Hypnum 

 dans les petites mares de Champlive." 



5. Selenastrum gracile Eeinsch. Hab. Sutton Park, War- 

 wickshire. (June, 1909.) Somewhat scarce in a small pool among 

 Scirpus fiuitans. Diam. cell. 2 }x ; apic. inter se distantibus 

 22-24 II. 



6. Tetraedron horridum W. & G. S. West in Journ. Eoy. 

 Micr. Soc. 1897, p. 502, t. 7, f. 4, 5. 



Hah. In ponds near Nuneaton, Warwickshire. (June, 

 1908.) 



This characteristic species occurred in great abundance along 

 with a few specimens of Opliiocytittm iMrvulum (Perty) A. Br. 



7. Pteromonas angulosa (Carter) Lemm. " Beitrage zur 

 Kenntniss der Planktonalgen V," Ber. Deutsch. Bot. Ges. xviii. 

 1900, p. 93. Gryptoglena angulosa Carter. Pteromonas alata 

 Cohn. Long. cell, sine integ. 16-9 /x, cum integ. 22 /x ; lat. cell, 

 sine integ. 13 /x, cum integ. 22 fx ; crass, cell. 8*2 /m. (Fig. 5, A 

 and B.) 



Hab. Earlswood Lakes, Warwickshire. (June, 1912.) 



No member of this genus has previously been recorded from 



the British Islands, possibly because they have been overlooked, 



but more probably because they are of decidedly rare occurrence. 



Only a few specimens were seen from the above-mentioned locality. 



* G. Hieronymus communicated his first account of Dicranochcete to the 

 Schlesischen Gesellschaft on Nov. 10th, 1887 ; subsequently he published "Ueber 

 Dicranochcete reniformis Hieron., eine neue Protococcacea des Siisswassers," 

 Cohn's Beitrage zur Biol, der Pflanzen, v. 1892, pp. 351-372, t. xi, xii. 



t M. J. Virieux, " Quelques x\lgues de Franche-Comte rares ou nouvelles," 

 Bull. vSoc. d'Histoire nat. Doubs, no. 21, Avril, 1911, p. 3. 



