COSMARIUM. 151 



Cells large, scarcely twice as long as broad, deeply 

 constricted, sinus widely open from an acute apex ; 

 semicells globose ; cell-wall densely covered with 

 bluntly conical warts except for a small area at the 

 apex, between the warts finely punctate. Chloro- 

 plasts parietal, with 4-6 bands in each semicell. 



Zygospore unknown. 



Length 97-2-104^; breadth 56-61'2/i; breadth of 

 isthmus 23-23-4 /u. 



SCOTLAND. --Near the Spittal of Glen Shee, Perth 

 (Roy fy Bis sett). 



Geonr. Distribution. Norway. Sweden. Bornholm. 



t/ e/ 



Finland. INT. Russia. Greenland. 



This species lias a most astonishing resemblance to the side 

 view of Cosmarium Brebissonii, agreeing in the conical warts 

 (or granules), in the bare place at each apex,, and in the fine 

 punctnlation of the cell-wall. The form mentioned by 

 Borgesen as occurring in Bornholm possessed hollow granules, 

 a feature not mentioned by Lundell as occurring in Swedish 

 specimens. 



NOTE: Cosmarium sphaericum Benn. ('Alg. N. Cornwall/ 

 1887, p. 17, t. 4, f. 22; Cooke'Brit. Desm/ 1887, p. 189, 

 t. 65, f. 5) appears to be the side view of a large Cosmarium, 

 such as C. Brebissonii or C. margaritatum. Lagerheim has 

 placed it as C. praegrande Lund. var. sph&ricum, but we do 

 not think there is sufficient evidence for regarding it as a 

 form of C. praegrande. Judging by the extraordinarily 

 inaccurate observations made by Bennett on various species 

 of Desmids, we have little hesitation in regarding his pub- 

 lished description and figure of " C. sphsericum" as merely 

 an erroneous interpretation of the side view of some large 

 species of Cosmarium. 



151. Cosmarium ornatum Ralfs. 

 (PL LXXVIII, figs. 1-10.) 



Cosmarium ornatum Ealfs, in Ann. Mag. Xat. Hist, xiv, 1844, p. 392, 1. 11, 

 f . 3 ; Hass. Brit, Freshw. Alg. 1845, p. 364, t. 86, f . 3 ; Ealfs, Brit. 

 Desm. 1848, p. 104, t, 16, f . 7 ; Kiitz. Spec. Alg. 1849, p. 176 ; Arch, in 

 Pritch. Infus. 1861, p. 734 ; Kabenh. Flor. Europ. Alg. Ill, 1868, p. 169 ; 

 Lund. Desm. Snec. 1871, p. 28; Kirchn. Alg. Schles. 1878, p. 153; 

 Wolle, Desm. U. S. 1884, p. 82, t. 18, f . 39-42 ; t. 49, f . 23, 24 ; Cooke, 

 Brit. Desm. 1887, p. 112, t, 40, f. 4 ; Hansg. Prodr. Algenfl. Bohni. 1888, 



