SOME NOETH AMERICAN DESMIDIEJS. 231 



4. Sph.^hozosma ixcavatum, Ealfs, Brit. Desm. p. G7, t. G. fig. 2. 

 Var. (PI. XII. fig. 9.) 



Long. 8-5-10 lii ; lat. cum apic. 9-5-10-5 ^ ; lat. isthm. 4-8-5'5 ^. 



Only one filament of this variety was seen ; it has a tubercle on each lateral margin 

 of each semicell similar to those on S. indicum, W. B. Turn. [Freshw. Alg. of E. India, 

 p. 141, 1. 18. fig. 2 (= *S'. excavatum, var. y, G. C. Wall, in Ann. & Mag. Nat. Hist. ser. II [. 

 V. (1860) p. 192, t. 7. fig. 16)]. 



Genus Spondylosium, Breb. 



5. S. PULCHRUM, Arcli. in Pritcb. Infus. ed. IV. p. 724. (Sphccrozosma pulchrtim. Bail. 



in Ealfs, Brit. Desm. p. 209, t. 35. fig. 2.) 



Var. INPLATUM, nobis. {Sphcerozosma pulchrum, Bail., var. injlatum, Wolle, Desm. 

 U.S. p. 29, pi. 49. fig. 8.) Porma apicibus cellularum minus productis ; a vertice 

 visis constrictionibus duabus, parte central! paene circulari, partibus lateralibus 

 majoribus et ovalibus. 



Long. cell. 34-40 ^; lat. 58-73 /u ; lat. isthm. 14-19o fx ; lat. apic. 10-13-5 /*; cmss. 

 (part, centr.) 16 ^. (PL XII. fig. 10.) 



Var. CONSTRICTUM, nobis. {Sph(«rozosma pulchrum, Bail., var. constricfum, Wolle, Alg. 

 U.S. p. 22, pi. 59. fig. 12.) (PI. XII. figs. 11, 12.) 



Long. 50-58 /i ; lat. 86-96 ^ ; lat. isthm. 23-26 ^ ; lat. apic. 1 9-21 n. 



All the specimens of this variety observed were not so stiffly and geometrically con- 

 stricted as Wolle figures them, and the sinus was more open on account of the constrictions 

 being nearer the lateral angles of the semicells. 



6. S. KECTANGULAiiE, nobis. {SphcBrozosma rectangulare, Wolle, Desm. U.S. p. 31, pi. 19. 



fig. 9 ; Sphcerozosma Gcebelii, Racib. in Flora (1895), i. p. 32, tt. 3, 4. fig. 5. 

 (Pi. XII. figs. 13, 14.) S. magnum, filis non tortis, sine vagina mucosa; cellulse 

 compressa3, 3-plo latiores quam longiores, profundissime constrictae, sinu angus- 

 tissimo-lineari ad extremum subampliato; semiccllulis transverse et anguste 

 oblongo-rectangulares, dentibus duobus divergentibus ad angidos marginis late- 

 ralibus uniuscujusque et dente singulo intra marginem ad medium, apicibus 

 rectis (retusis in medio [Wolle]); a latere visae semicellulae depresso-globosa^ 

 cum dente divergente ad marginem lateralem unuraquemque ; pyrenoidibus binis 

 in semicellula unaquaque. 

 Long. 19-23^; lat. sine dent. 56-61 ^i; lat. cum dent. 61-66^; lat. isthm. 10-5-12-5^; 

 crass, cum dent. 17-19 /i. 



The plant described and figured by Wolle as Sjihccrozosnui rectangulare certainly 

 belongs to the genus Spondylosiutn : there is no doubt that the plant we have found is 

 the same species as that which Wolle had under observation, but the compressed cells 

 have truncate closely apjplied apices and deutigerous lateral margins. The filaments 

 are not twisted like those of Spondijlosium pulchrum- So far as could be observed in the 

 preserved specimens examined, the chlorophyllaceous mass in each semicell contamed 

 tAvo pyrenoids, oval or elliptic in form, which were directed obliquely downward towards 



2k2 



