160 BRITISH DESMIDIACE^. 



155. Cosmarium Turner! Roy. 

 (PL LXXIX, figs. 8, 9.) 



Cosmarium margaritiferum Ealfs, Brit. Desm. 1848, t. 33, f. 6 b. 



C. Turneri Roy, Freshw. Alg. Enbridge Lake and Vicin. 1S90, p. 337. 



Cells of medium size, a little lonsrer than broad, 



' o 



deeply constricted, sinus narrowly linear with a very 

 slightly dilated apex ; semicells elliptic- subreniform. 

 Side view of semicell subcircular. Vertical view 

 elliptic. Cell-wall granulate, grannies of uniform 

 size (or very slightly reduced in size above the isthmus) 

 and disposed in indistinct oblique series, about 20-23 

 visible at the margin of each semicell. 



Zygospore globose, furnished with short furcate- 

 emarginate spines, each of which arises from a large 

 conical base. 



Length 56-58 n ; breadth 51-53 p ; breadth of 

 isthmus 14-16 jit; thickness 28^; diam. zygosp. with- 

 out spines 53^, with spines 74^. 



ENGLAND.- -Enbridge Lake, Hants (Rot/). 



IRELAND.- -Lough Grartan, Donegal ! 



We are unable to give the locality from wliicli Ralfs 



t/ 



obtained specimens and zygospores of this plant, as that 

 author did not discriminate between the different species 

 which he included under the name " Gosmariiim margariti- 

 ferum" We have ourselves only once observed a Cosmarium 

 which we could with any degree of certainty refer to 

 C. Turneri Rov. This specimen we have figured (PI. LXXIX, 



fi '- 9 )- 



C. Turneri differs from C. margaritiferum in the form of its 

 semicells, in the nature of its granulation, and in its spiny 

 zygospore. It differs from C. reniforme in its less reniform 

 semicells, with fewer and more distant granules, and in its 

 spiny zygospore. 



Hansgirg has farther complicated the synonymy of the 

 genus by naming a form of C. Pseudobroomei as " Cosmarium 

 Turneri'' (ride Hansgirg in ' Sitzimgsber. d. k. bohm. Ges. d. 

 Wissensch. math. nat. C\. } 1902, p. 101 [ Cosmarium sp. 

 Turn. ' Freshw. Alg. E. India/ 1893, p. 72, t. 23, f. 10]). 



