BRITISH DESMIDIACE^. 



SCOTLAND.- -Sutherland ! Harris and Lewis, Outer 

 Hebrides ! 



IRELAND.- -Acliill Island, Mayo ! Carrantuohill, 

 Kerry ! 



Geogr. Distribution. Uruguay. 



This small form appears to be more frequent than the type. 

 It somewhat resembles C. annulatum var. vlegans, but the 

 horizontal series of bigranulate warts are situated closer 

 together, and the convex, verrucose apex is quite distinctive. 



We have described from the United States a var. simplicius 

 of C. elegantissimum in which the warts are entire, rounded 

 elevations (Of. W. & G. S. West, 'Some Desm. U. S.' 1898, 

 p. 308, t. 17, f. 7). This form also has the hemispherical 

 poles so characteristic of all forms of C. elegantissimum. 



246. Cosmarium tuberculatum Arch. 

 (PL XCVII, figs. 9-11.) 



Cosmarium tuberculatum Arch. Descript. New Cosm., etc., 1863, p. 247, t. 



12, f. 11-15 ; Eabenh. Flor. Europ. MO; III, 1868, p. 178 ; Roy & Biss. 



Scott. Desm. 1894, p. 177 ; W. & G. S. West, Alga-fl. Yorks. 1900, p. 95. 

 Calocylindrus tuberculatus (Arch.) Cooke, Brit. Desm. 1887, p. 123, t. 43, 



f. 15 ; West, Alg. N. Yorks. 1889, p. 293. 

 Disphinctium tuberculatum De Toni, Syll. Alg. 1889, p. 892. 



Cells minute, about lj times longer than broad, 

 moderately constricted, sinus widely open and shallow, 

 forming an obtuse angle ; semicells elliptic-hexagonal, 

 the upper convex margin bordered by 5-7 (usually 0) 

 minute and rather depressed granules. Side view of 

 semicell ovate-elliptic, with the upper convex margin 

 furnished with 5-6 granules. Vertical view broadly 

 elliptic, with 6-7 granules round the margin. 

 Chloroplasts . . . . ? 



Zygospore unknown. 



Length lo-lS'o/i; breadth 12-1 4 /A; breadth of 

 isthmus 7-8 /i ; thickness 7'5-8'5 JJL. 



ENGLAND. Mickle Fell, 1S T . Yorks ! 



SCOTLAND.- -Scotston Moor, Aberdeen; Durris, 

 Kincardine ; between Loch Lomond and the head of 

 Loch Long, Dumbarton (Boy ^ Jttssrtt). 



IRELAND.- -Dublin and Wicklow (Archer). 



