168 BRITISH DESMIDIACE/E. 



The Desmid figured by Wolle (' Desm. U.S.' 1884, t. 15, 

 f. 22) as C. bioculatum is most probably a form of (7. tenue as 

 it lias a smooth zygospore. Johnson ('Rare Desm. U.S/ I, 

 1894, p. 288) also states that C. tenue is common almost 

 everywhere in the United States, and is often found in 

 quantity and usually with zygospores. 



26. Cosmarium tinctum Ralfs. 

 (PL LXI, figs. 16-18.) 



Cosmarium tinctum Ralfs, Brit. Desni. 1848, p. 95, t. 32, f. 7 ; Arch, in 

 Pritch. Infus. 1861, p. 731 ; Kirchn. Alg. Schles. 1878, p. 148 ; Wolle, 

 Desm. U.S., 1884, p. 61, t. 16, f. 31 ; Cooke, Brit. Desm. 1886, p. 90, t. 37, 

 f . 7 ; Hansg. Prodr. Algenfl. Bohrn. 1888, p. 248 ; De Toni, Syll. Alg. 

 1889, p. 942 ; West, Alg. N. Wales, 1890, p. 288 ; Alg. W. Ireland, 1892, 

 p. 146 j Alg. Eng. Lake Distr. 1892, p. 725 ; Eoy & Biss. Scott. Desm. 

 1894, p. 176; Nordst. Index Desm. 1896, p. 255; West & GL S. West, 

 Alg. S. England, 1897, p. 486; Alga-fl. Yorks. 1900, p. 73 ; Alg. N. Ireland, 

 1902, p. 34. 



Sphserozosma tinctum Eabenh. Flor. Europ. Alg. Ill, 1868, p. 150. 



Ursinella tincta Kuntze, Revis. gen. plant. 1891, p. 925. 



Cells minute, a little longer than broad, moderately 

 constricted, sinus narrow towards the apex but open 

 outwards; semicells elliptic. Side view of semicell 

 subcircular. Vertical view elliptic, ratio of axes about 

 1 : 1*8. Cell-wall smooth and of a reddish-brown 

 colour. Chloroplasts axile, with one pyrenoid. 



Zygospore subquadrate, with rounded angles and 

 retuse sides ; cell- wall smooth. 



Length 10-15^; breadth 7'5-ll'6^; breadth of 

 isthmus 4*5-8*4 ^t; thickness 5-9 /u ; cliam. zygosp. 

 11-15/4. 



ENGLAND. Cumberland ! Westmoreland ! W., IN"., 

 and E. Yorks ! Cheshire (Roy). Essex ! Warwick 

 (Wills). Surrey! Sussex (Ralfs). Kent! Hants! 

 Devon ! Cornwall ! (Ralfs). 



WALES. Fairly general in Carnarvonshire ! 



SCOTLAND. --General ! Zygospores from Aberdeen 

 and Kincardine (Roy $ Bissett). Outer Hebrides ! 

 Shetlands ! 



IRELAND.- -Donegal ! Mayo ! Galway (zygospores 

 from near Eoundstone) ! Kerry ! Dublin and Wicklow ! 

 (Archer). Armagh ! 



