ROYA. 107 



vacnole within each apex, the extremity of the chloroplasl 

 falling short of the apex and being- almost invariably liolluu-,,1 

 for this purpose. We are inclined to believe that the absence 

 of the moving gypsum-corpuscles in the apical vacuoles of a 

 ClnNfi-riitiii is a very abnormal feature, and one which has 

 been produced by pathological conditions. There is not the 

 slightest trace of apical vacuoles in the genus lfoj/n } and the 

 extremities of the chloroplasts are courc^ in order to fit as 

 closely into the rounded ends of the cell as possible. Other 

 differences from the vast majority of Closteria are in the 

 lateral position of the nucleus, which is lodged in a special 

 excavation of the chloroplast, and in the almost entire absence 

 of attenuation of the cells. 



There are only three described species, all of which are 

 rare British Desmids. 



1. Roya obtusa (Breb.) West & G-. S. West, 

 (PI. X, fig. 27.) 



CIost>:rium obtnsum Brib. Liste Dosm. 1850, p. 154, t. 2, f. 46; Arch, in 



Pritch. Infns. 1861, p. 746; Eabenh. Flor. Europ. Algar. Ill, 1868, p. 



103; Kirchn. Beitr. Algenfl. Wiirtemb. 1880, p. 173; Wolle, Desm. 



U. S. 1884, p. 38, t. 6, f . 1 ; Cooke, Brit, Desm. 1886, p. 19, t. 10, f . 4 ; 



West. Alsf. N. Wales. 1890, p. 284; Alo-. W. Ireland, 1892, p. 121 : 



Nordst, Index Desm. 1896, p. 186. 

 Closterium obtusum a. typicum Klebs, Desm. Ostpreuss. 1879, p. 8, t. 1, 



f. 2 a et I. 



Closterhnn obtusum b. major Racib. Nonn. Desm. Polon. 1885, p. 63. 

 ArtJtroJia obtusa Kvmtze Kevis. Gen. Plant, 1891, p. 883. 

 Roya obtusa iBreb.) West & G. S. West, New and Int. Freshw. Alg. 1896, 



p. 152 ; Some Desm. U. S. 1898, p. 282 ; Alga-fl. Yorks. 1900, p. 48. 



ls small, cylindrical, 4-10 times longer than their 

 diameter, very slightly curved, apices obtusely rounded; 

 with 4-8 pyrenoicls in the chloroplast. 



Zygospore globose and smooth (according to 

 Kirehner). 



Length 75-148 /< ; breadth 9-15 /.<. 



ENGLAND. Greetland and Cullingworth, \V. Yorks ! 

 Strensall, E. Yorks! Epping Forest, Essex! E slier 

 West-end Common, Surrey ! Enbridge Lake, Hants 

 (Rny). 



WALES. Cap el Curig, Carnarvonshire ! 

 SCOTLAND. Ross, Aberdeen, Inverness, Kincardine, 

 Perth, Argyll (Roy & Piswtt). 



