OF THE DESMIDIE^. 



737 



2 * Segments ivitli a single acute tooth or 

 spine at each side, 



A. minufus (Kg.). — Frond very mi- 

 nute, smooth, two or three times longer 

 than broad ; constiiction a minute acute 

 notch ; segments narroiv, lateral margins 

 parallel, ends roimdly concave, ano-les 

 slightly produced into minute spines 

 dii'ected upwards. F., G. 



A. Pittacium (Breb. sp.). — Frond mi- 

 nute, smooth, two or three times longer 

 than broad ; constriction a minute acute 

 notch ; segments very slightly injlated at 

 the base, sides curved, end margin roundly 

 concave, angles acute. = Euastrum Pit- 

 tacium (Breb.). F. 



A. Incus (Hass.). — Frond minute, 

 smooth, as long as or longer than broad ; 

 constriction a deep notch or sinus ; seg- 

 ments mth inner margin turgid, outer 

 truncate, spines subulate, acute. Sporan- 



gium orbicular, spinous ; spines subulate. 

 G.B., I., F., G., U.S.A. a, segments 

 somewhat semiorbicular, connected by 

 a distinct neck, spines diverging. L. 

 i 1-1100" to 1-1660" ; B. 1-1960" to 

 1-1420". ^3, segments gibbous near the 

 base, spines parallel or converging, (ni. 

 \ 36.) L. 1-833" ; B. 1-1116". 

 j A. subulatus (Kg.). — Frond minute, 

 ! smooth, about as long as broad; con- 

 [ striction a wide acute-angled notch ; 

 segments hroadly fusiform, spines hori- 

 zontal, straight, slender, subulate; ends 

 convex. G., U.S.A. 



A. convergens (Ehr.). — Frond smooth, 

 broader than long ; constriction deep, 

 I acute ; segments elliptic, each having its 

 lateral spines curved towards those of the 

 ' other; ends convex. L. 1-1539" to 1-598"; 

 j B. 1-1477" to 1-584:" .■= Staurastrum con- 

 , vergens (Menegh.), Euastrum convei'gens 

 \ (Nkg.). G.B., L, R, G., U.S.A. 



Genus STAUE.ASTRUM (Meyen). — Frond more or less deeply constricted 

 at the middle ; segments broader than long, often provided with spines or 

 processes ; end view angular or radiate, or circular luith a lohato-radiate 

 margin, or very rarely compressed with a process at each extremity. 



* Segrnents inf. v. with each of the oppo- 

 site lateral extremities furnished ivith a 

 mucro or a simple subulate acute awn 

 or spine, ivhich in e. v. terminates the 

 angles, and without others intermediate. 



t Segments smooth, angles in e. v. 

 inflated, sides concave. 



Staueastruim dejectum (Breb.). — Seg- 

 ments in f. V. lunate or elliptic, smooth, 

 mucrones or awns directed upwards, pa- 

 rallel or convergent ; e. v. with three or 

 four angles, angles injlated, mammillate, 

 terminated by a mucro or awn, sides 

 concave at the centre. Sporangium or- 

 bicular, at first covered with minute hair- 

 like spines, afterwards beset with stout 

 subulate spines, and placed between the 

 deciduous empty fronds. L. 1-833" ; B. 

 1-757".= Goniocystis (Trigonocystis) mu- 

 cronata (Hass.). a, segments externally 

 lunate, awns directed outwards ; /S, seg- 

 ments elliptic, awns parallel ; y, awns 

 converging. G.B., I., F., U.S.A. 



S. apiculatum (Breb.). — Segments in 

 f. V. somewhat turbinate, smooth, oppo- 

 site lateral extremities rounded, external 

 margin straight, furnished at each side on 

 the upper outer margin 7iear the lateral 

 extremities with a simple, short, subulate, 

 acute spine directed upwards ; e. v. with 

 three angles, angles inflated, mammillate, 

 terminated by a short acute spine, sides 



concave. Sporangium orbicular, beset 

 with conical spines, enlarged at the base 

 and obtuse at the apex. F. 



S. Dickiei (Ralfs). — Segments in f. v. 

 subelliptic, turgid, smooth ; spines short, 

 curved, acute, converging with those of 

 the opposite segment; e. v. with three 

 angles, angles injlated, roimded, termi- 

 nated by a spine, sides concave at the 

 centre. L. 1-855" ; B. 1-929". G.B.,I.,F. 

 j S. brevispina (Breb.). — Segments in f. v. 

 I elliptic or somewhat reniform, very tur- 

 , gid, smooth ; mucrones minute, iticonspi- 

 cuous; e. v. with three angles, angles 

 inflated, broadly rounded, terminated by 

 an inconspicuous mucro, sides concave at 

 the centre. L. 1-502" ; B. 1-510". G.B., 

 L, F. 



S. cuspulntum (Breb.). — Segments in 

 f V. fusiform, or truncate on outer mar- 

 gin, connected by a long narrow bandy 

 smooth ; awns subulate, straight, acute, 

 parallel or somewhat converging ; e. v. 

 with three or four angles, angles inflated, 

 mammillate, terminated by an awn, sides 

 j concave at the centre. Sporangium or- 

 I bicular, covered all over by the enlarged 

 ! bases of the few spines, which are iilti- 

 I mately much attenuated and acute. L. 

 I 1-883" ; B. 1-1000". (i. 31-34.) = Phijc- 

 I astrum cuspidatum (Kg.), P. spinulosum 



(Niig.). G.B., I., F., G., Italy. 

 I S. aristiferum (Ralfs). — Segments 

 3 B 



