242 BRITISH DESMIDIACE^E. 



** Ca.vities between cells absent, or not readily visible. 

 f Semicells angular in vertical view. 



3. D. Occident ale. 



4. D. Swartzii. 



ft Semicells circular or elliptical in vertical view, often 

 with opposite mamillse. 



5. D. cylindricum. 



6. D. coarctatum. 



7. D. gracileps. 



8. D. qiiadratum. 



i 



1. Desmidium Aptogonum Breb. 

 (PL CLXIV, figs. 1-3.) 



Desmidium Aptogonum Breb. Alg. Falaise, 1835, p. 65, t. 2 ; Menegh, 

 Synops. Desm. 1840, p. 3 (sep.) ; Kiitz. Phyc. Germ. 1845, p. 141 ; 

 Spec. Alg. 1849, p. 190 ; De Bary. Conj. 1858, p. 76, t. 6, f. 55, 56 ; Arch, 

 in Pritch. Inf. 1861, p. 723, t. 3, f. 7, 8; Eabenh. Krypt.-fl. Sachs. 1863, 

 p. 181 ; Reinsch, Alg. Frank. 1867, p. 206 ; Rabenh. Flor. Eur. Alg. 

 1868, p. 154; Kirchn. Alg. Schles. 1878, p. 132 ; Wolle, Desm. U.S. 1884, 

 p. 27, t. 2, f. 6, 7, t. 49, f. 7 ; Cooke, Brit. Desm. 1887, p. 11, t. 5, f . 1 ; 

 Hansg. Prodr. Alg. Bohm. 1888, p. 172; Hauptfl. Zellm. u. Hiillgall.Desm. 

 1888, pp. 20, 51, t. 2, f. 6, 10-15 ; De Toni, Syll. Alg. 1889, p. 781 ; West, 

 Alg. N. Wales, 1890, p. 7 ; Alg. W. Ireland, 1892, p. 117 ; Turn. Freshw. 

 Alg. E. India, 1893, p. 147; Roy & Biss. Scott, Desm. 1893, p. 9; West 

 & G. 8. West, Some N. Amer. Desm. 1896, p. 233, t. 12, f. 24 ; Desm. 

 U. States, 1898, p. 320 ; Comere, Desm. de France, 1901, p. 201, t. 16, 

 f. 10 ; West & G. S. West, Alga-fl. Yorks. 1902, p. 110 ; Alg. Ceylon, 1902, 

 p. 193 ; Alg. Burma ; 1907, p. 226 ; Georgev. Desm. Macedon. 1910, 

 p. 237 ; Borge, Sao Paulo Alg. 1918, p. 75. 



Aptogonum Desmidium Ralfs, Brit. Desm. 1848, p. 64, t. 32, f. 1 a-d ; 

 Breb. Liste Desm. 1856, p. 119 ; Delp. Spec. Desm. subalp. 1873, p. 61, 

 t. 3, f. 1-5 ; Hustedt, Desm. et Bac. Tirol, 1911, p. 341. 



Desmidium Swartzii Wallich, Desm. low. Bengal, 1860, p. 189, t. 7, f. 1, 4. 



Desmidium Swartzii var. amblyodon West & G. S. West, Alg. Madagascar, 

 1895, p. 43, t, 9, f. 34, 35. 



Cells of medium size, about twice as broad as long, 

 constriction not deep, but open and acute ; semicells 

 narrowly oblong, lateral angles broadly rounded, apex 

 broad and concave in the middle, but produced at the 

 angles to form fairly long connecting processes, so that 

 a cavity of considerable size is left between the ad- 

 jacent cells ; in end view usually triangular, sometimes 

 quadrangular, angles very broadly rounded, sides con- 

 cave ; chloroplasts axile, one in each semicell, with a 

 massive lobe radiating from the centre into each angle, 

 and a pyrenoid embedded in each mass. Filaments 



