13 



5. Chætoceros decipiens, Cl. (1873. 13) p. 11, T. I. %. 5. 



Tab. nostr. I, fig. 2, ;i, T. III, fig. 34. 

 Sjn. Ch. decipiem v. concrcta, Gruii. (18S0) p. 120. 

 „ concretum, Gruii. in Eiiglor (1883) p. XI. 

 „ Ch-Hnowii, Sohiitt (18i),')) p. 43, fig. 14 a, h. 



Kjederne rette, stive, flercellede, mere eller mindre 

 sammentrj'kte, 12 — 78 a lirede. 



Cellerne i frontstilling rektana;ulære med skarpe, ofte 

 fremspringende hjorner. Ska lierne mere eller mindre kon- 

 kave, foramina cirkulære, ovale eller næsten spaltefoi-mede, 

 med svag indsnøring paa midten. Baandets Irengde variabel, 

 omkring ' '3 af cellens længde. 



Cellekjerne og kromatotorer vægstillede, kromatofo- 

 rerne pladeformede, t\>rhoklsvis store, 4 — 10 i hver celle. 



Cellerne berorer hverandre med skarpe hjorner, fra 

 hvilke hornene gaar nd i .sagittal retning, sammenvoksede 

 paa en kort strækning; derefter divergerer de svagt bue- 

 formig i transversal retning, symmetrisk i forhold til sagit- 

 talplanet, afboies desuden longitudinalt i retning af fila- 

 mentets nærmeste ende. 



Termiiialhorn skarpt differentierede, kortere og tyk- 

 kere end de andre, stribede paa tværs; de gaar ud i sagit- 

 talplanet i skråa retning, af bøies derefter mod longitudinal- 

 aksen, saa at de liliver næsten parallele med denne. 



Hvilesporer ukjendte. 



Varierer meget især med hensyn til cellevæggens og 

 hornenes tykkelse og formen af foramina. Som yderformer 

 kan adskilles: 



/. hiemalis, Gran mscr. T. I, fig. 2. 



Cellevæggen sterkt forkislet, tyk. hornene tykke, fora- 

 mina smale, næsten spalteformede med svag indsnøring paa 

 midten. Vegeterer især i februar — marts. 



/. internipta, Gran mscr. T. III, fig. 34. 



Svagere forkislet, hornene tynde, skallerne sterkt kon- 

 kave, foramina i de smaleste kjeder cirkulære, hos de bre- 

 dere mere eller mindre langstrakt ovale. Vegeterer især 

 om sommeren. 



Cli. decrpiens er den almindeligste af alle vore arter, 

 vegeterer til alle aarstider og findes næsten overalt ved 

 vore kyster, om end ofte sparsomt. 



Vdhreddse. N. Atlanterhav i store mængder. Isha- 

 vet, Kordsøen, Skagerak— Østersøen (Engler, Schiitt). 



6. Chætoceros teres. Cl. (1896, 5) p. 30, fig. 7. 



Tab. III, fig. 3r)— 3G. 

 Kjederne rette, ikke snoede, omtrent cylindriske, 18 

 — 48 ^i brede. Cellerne i frontstilling rektangulære med 

 skarpe hjørner, oftest længere end filamentets bredde, i 

 sidestilling cirkulæro-elliptiske, i sagittalstilling forlænget 

 elhptiske. 



5. Chætoceros decipiens, Cl. (1873, 13) [). II, Pl. I, fig. o. 



Pl. I, figs. 2, 3; Pl. III, fig. 34. 

 Syn. Ch. decipiens v. concreta, Grun. (1880) p. 120. 

 „ concretum, Grun. in Engler (1883) p. XI. 

 „ Grumm-it, Schiitt (180.')) p. 43, fig. 14, a, b. 



Filaments straight, stifl", multicellular, more or less 

 compressed, 12 — 78 u wide. 



Cells, in a front view, rectangular, with sharp, often 

 projecting angles. Valves more or less concave, foramina 

 circular, oval or almost linear, witii slight constriction in 

 the niiddle. Lengtii of the hoop variable, aViout ' ;., that of 

 the cell. 



Nucleus and chromatophores situateil in the wali; 

 chromatophores lamelliform, comiiaratively large, from 4 to 

 10 in each cell. 



The cells touch one anotiier with siiarp angles, from 

 wliicli the setæ issue in a sagittal dircction. coalesced for 

 a short distance, afterwards diverging, with a slight curve, 

 in a transverse direction, symmetrically in relation to the 

 sagittal plane, being moreover, deflected longitudinally in the 

 direction of the nearest end of the filament. 



Terminal setæ sharply differentiated, shorter and 

 thicker than the others, striated transversely ; they spring 

 from the sagittal plane in an oblique direction, being after- 

 wards detlected towards tiie longitudinal axis, thereliy be- 

 coniing almost parallel with it. 



Spores nnknown. 



Varies greatly, especially witji regard to the thickness 

 of the cell walls, and the shape of the foramina. As ex- 

 treme forms the foUowing may be specially mentioned : 

 /'. Memalis, Gran mscr. Pl. I, fig. 2. 



Cell walls very siliceous, thick; setæ thick; foramina 

 narrow, almost linear, with slight constriction in the niid- 

 dle. Vegetates more especially in Pebruary and March. 

 /. hdcrrujita, Gran mscr. Pl. III, fig. 34. 



Less siliceous, setæ thin, valves deeply concave, fora- 

 mina in the narrower cells circular, in the broader, more 

 or less of an elongated oval shape. Vegetaties more espe- 

 cially in tiie summer. 



Cli. decipiens is the commonest of our (Norwegian) 

 species, vegetates at all seasons of the year, and is found 

 almost everywhere on our (Norwegian) coasts, though often 

 sparingly. 



Distrihdion. N. Atlantic Ocean in great (juantities; 

 Arctic Ocean, North Sea, Skagerak, Baltic (Engler, Schiitt). 



6. Chætoceros teres, Cl. (1896, 5) p. 30, fig. 7. 



PL III, figs. 3,i, 30. 

 Filaments straight, not twisted, almost cylindrical, 

 18 — 48 (.1 wide. Geils, in a front view, rectangular with 

 sharp angles, often longer than the width of the filament; 

 in a side view, circular to elliptical; in a sagittal view, 

 elongated elliptical. 





*^ LIS R A 



