SPH^ROZOSMA. 209 



true warts do not occur in this species any more than in Sph. 

 vertebratum Ralfs, but that it is the hardened ends of gelatinous 

 strands exuding from 2 horizontal rows of pores which are often 

 visible even in the unstained cells. This is a good suggestion, 

 since the so-called granules are very delicate and often difficult 

 to see. From these considerations it would seem that Sph. 

 Aubertianum and its var. Archeri are quite possibly synonymous. 



2. Sphaerozosma vertebratum (Breb.) Ralfs. 

 (PL CLIX, figs. 9, 10.) 



DesmidiiiHi vertebratum Breb. Alg. Falaise, 1835, p. 269, t. 2. 



Isthmia vertebrata Menegh. Synops. Desm. 1840, p. 205. 



Desmidium compression Ralfs in Ann. Mag. Nat. Hist. vol. 9, 1842, p. 253. 



Isthmo&ira vertebrata Kiitz. Phyc. Germ. 1845, p. 141 ; Spec. Alg. 1849, 



p. 188. 



Sphcerozosma unidentata Ralfs in Ann. Mag. Nat. Hist. vol. 16, 1846, p. 14. 

 Sph. verttbrntiini Ralfs, Brit. Desm. 1848, p. 65, t. 6, f. 1, t. 32, f. 2 : De 



Bary, Conj. 1858, p. 45, t, 4, f. 32-34 ; Arch, in Pritch. Inf. 1861, p. 724, 



t. 1, f. 15-17; Rabenh. Krypt.-fl. Sachs. 1863, p. 178; Jacobs. Desm. 



Danem. 1875, p. 211 ; Kirchn. Alg. Schles. 1878, p. 133 ; Wolle, Desm. 



U. S. 1884, p. 30. t, 4, f. 13 ; Cooke, Brit, Desm. 1887, p. 3, t. 2, f. 1 ; 



Hansg. Prodr. Ahr. Bohm. 1888, p. 170 ; De Toni, Syll. Alg. 1889, p. 789 ; 



West, Alg. Engl. Lake Distr. 1892, p. 6 ; Roy & Biss. Scott. Desm. 1893, 



p. 10 ; Conn-re, Desm. de France, 1901, p. 199, t. 16, f. 12 ; West & G. S. 



West, Alga-fl. Yorks. 1902, p. 110; Liitkem. Zellmem. Desm. 1902, 



pp. 354, 366, t. 19, f . 8 ; G. S. West, Brit. Fre.slnv. Alg. 1904, p. 175, 



f. 67 ('. 



Cells small, about as long as broad, or sometimes a 

 little broader, constriction fairly deep, sinus narrow, 

 linear, obtuse at the apex ; semicells nearly oblong or 

 subreniform, slightly narrower at the apex ; lower 

 margin nearly straight, upper angles very rounded, apex 

 flattened ; lateral view of cell oblong, slightly con- 

 stricted in the middle, semicells short and oval ; apical 

 processes median ; cell-wall smooth. Chloroplasts axile, 

 with a central pyrenoid in each semicell. 



Zygospore smooth and spherical (Ralfs). 



Length 19(Ji; breadth 21-24 u ; thickness 12 \L ; 

 breadth of isthmus 9-1 0[/. ; diam. zygospore 21 \L. 



ENGLAND. - Bassenthwaite Water, Cumberland ! 

 Westmoreland! (Ralfs). Rawcliffe Common and Ingle- 

 borough, W. Yorks ! Strensall Common (W. B. Turner) 

 and Pilmoor. N. Yorks ! Riccall Common, E. Yorks ! 



VOL. V. 14 



