'24 



SYSTEMATIC HISTORY OF TIIE IXFUSORIA. 



appearance to the filament, united to each other by minute tubercles or gland 

 lihe processes. 



Sph^rozosma rertehratum (Ralfs) 



Joints as long as broad, constriction deep, 

 aeute ; segments reniform, giand-like 

 processes oblique, solifari/ at the centre of 

 each margin. A gelatinous sheatli evi- 

 dent. Sporangium spherical, smooth, 

 placed between the empty segments, the 

 lilament previously to conjugation break- 

 ing up into single joints. L. 1-1429"; 

 B. 1-909" to 1-666". (i. 1^-17. ) = Sph. 

 elegans (Corda, Hass.), OdonteUa loii- 

 dentata (Elir.), Isthniia vertebrata 

 (Menegh.), Isthmosira vert. (Kg.). G.B., 

 I., F., G., Italy, U.S.A. 



S. excavation (Ralfs). — Joints longer 

 than broad, subquadrate, very minute; 

 constriction a deep rounded sinus on 

 both sides, and ftvo sessile f/land-like pro- 

 cesses on each mare/ in at their junction; 



Genus SPONDYLOSIUM (Breb.)- 

 joints deeply divideel on each side, thus 

 pinnatifid appearance to the filament, 

 processes. 



STO'N'DY'LOBiV'Msto7nato7norpha7n('BY.). 

 — Joints about one-third broader than 

 long, constriction deep, segments reni- 

 form, ends brocully rounded; no sheath. 

 ' z= Isthmia stomatomorpha (Menegh.). F. 



S. pulchrum (Bail. sp.). — Joints twdce 

 as broad as long, constriction not deep, 

 acute, segments elliptic ; junction margins 

 ^t\i{\o[h.i, forming short connecting bands ; 

 gelatinous sheath wide. = Sphcerozosma 

 pulchrum (Bail.). U.S.A. 



S. imlehellum (iVrcher). — Filament 

 minute, fragile ; joints about as broad as 

 long, sharply incised ; segments laterally 

 infiated ett the base, thus giving a pouting 

 appearance to the joint, mtr rowing to 

 the ends, which are streiight, with square 

 angles ; endochrome containing in each 

 segment a single, central, lighter- 

 colom-ed, globular corpuscle. No evi- 

 dent gelatinous sheath. L. 1-2330" ; 



angles sometimes with three very minute 

 teeth ; no evident gelatinous sheath. 

 Sporangium elliptic, placed between the 

 empty joints, the tilament previously 

 breaking up. L. 1-2575"; B. 1-3050". 

 = Isthmosira excavata (Kg.). G.B., I., 

 F., U.S.A. 



S.^liforme (Ehr.). — Joints about as 

 long as broad ; constriction acute ; seg- 

 ments elliptic, and united by double 

 slender jyrocesses ivhich include a quadrate 

 foreimen between each pair. = Isthmosira 

 JUiformis (Kg.). G. 



S. lamelliferum (Corda). — Joints about 

 one-third laroader than long, constriction 

 deep, slightly rounded within ; segments 

 'ed, reniform ; connecting processes 



" flattened, 

 sheath. G. 



colomless ; a gelatinous 



-Filament compressed or ^-angular ; 

 forming two segments, and giving a 

 and without intermediate tubercles or 



B. 1-2330". (m. 10.) I. 



S. dejn-essum (Breb.). — Joints some- 

 what broader than long, suhquadrate, 

 constriction a rounded sinus, angles 

 rounded, ends straight, furnished at end 

 margin on upper surface with three 

 rounded protuberances ; " no sheath." 

 (III. 9.) F. 



S. serratum (Bailey, sp.). — Joints 

 broader than long, constriction a trian- 

 gular notch ; segments foiining lateral 

 triangular acute p)rojeetions, thus giving 

 a serrated outline to the filament ; junc- 

 tion margins straight. = Sphcerozosma 

 serratum (Bail.). U.S.A. 



S. secedens (De Bary, sp.). — Filament 

 very fragile, joints as long as broad, con- 

 striction a shallow rounded sinus ; seg- 

 ments subelliptic, ends concave ; no gela- 

 tinous sheath. L. 1-287"'. = Sphcerozosma 

 secedens (De Bary). G. 



B. Fronds simple, free, owing to complete transverse division. 

 1. Fronds distinctly constricted at the middle, never as much as three times 

 longer than broad. Sporangia mostly spherical and spinous or tubercu- 

 lated, or very rarely spherical or quadrate and naked. 



Genus TETRACHASTRUM (Dixon). — Frond compressed, deeply con- 

 stricted into two 3-lobed segments ; lateral lobes projecting horizontally, or 

 sometimes divergent, broadest at their base and simply atteiiuated outwards ; 

 end lobe laterally expanded into a horizontal attenuated projection on each 

 side, subtending the lateral lobes ; central constriction a gradually widening 

 incision {ab, c, vide supra). 



