258 



EXPLANATION OF THE PLATES. 



Plate VII. 



Fig. 1. Eiiastnim crassiim (Biéb.) Ralfs: a semicell in front view; c and 

 c' end view of semicells with more or less well-marked protu- 

 berances on each side of the semicells; 1' var. scrobiciilata Lund. 



Fig. 2. E. verrucosiim Ehrenb.: two difTerent forms of this species. 



Fig. 3. E. ampiillaceiim Ralfs var. scrobiculata Nordst. 



Fig. 4. E. inerme (Ralfs) Lund. 



Fig. 5. E. Lyngbyei nov. sp. 



Fig. 6. Cosmariiim perforatam Lund. var. rotnndata nov. var. 



Fig. 7. C. Schubelerii Wille. Formå. 



Fig. 8. C. pseiidopij ramidatiim Lund. *maxiina nov. subsp. 



Fig. 9. C. decedens Reinsch. 



Fig. 10. C. boreale nov. sp. 



Fig. IL Xanthidiiini aciilealiim Ehrenb. 



Fig. 12. — — — formå brevispina. 



Fig. 13. X. qimdricorniitiim Roy & Biss. formå longispina n. f. 



Fig. 14. Stanrastriim horametnim Ro}' & Biss. \ar. færoénsis n. v. 



Fig. 15. S. rostelhim Roy & Biss. 



Fig. 16. S. crcniilatiim (Nagl.) Delp. 



Fig. 17. S. Pseudosebaldi Wille. 



Fig. 18. Cosmariiim Regnesi Reinsch. 



Plate VIII. 



Fig. 1. Stanrastriim jaciiliferiim West: a cell with 3 spines on each 

 semicell seen in side view; b cell with 3 spines on the top 

 semicell and 4 on the bottom one seen in side and vertical 

 view; c two individuals formed by division, but not yet sepa- 

 rated from each other. One of the semicells of the topmost 

 individual has 2 spines marked 2) and the other 3 ; d, a two- 

 sided specimen seen in front, side and vertical view. 



Fig. 2. S. megacantha Lund. formå. 



Fig. 3. S. oxyacantha Arch. formå torta. 



Fig. 4. S. inconspiciiiim Nordst.: a several cells connected together; c 

 end view of a semicell. 



Fig. 5. Chætosphæridiiim Pringsheimii Kleb. forvna conferta K\eh.: a plant 

 with cells firmly bound together; b more loosely connected 

 piant, the connecting-tubes between the cells quite distinct; c 

 cells seen in side view; rf, e, f and g young individuals. 



Fig. 5. Enteromorpha micrococca formå siibsalsa Kjellm.: o portion of 

 thallus slightly magnified; b a thin fdament more highly mag- 

 nified; c portion of thallus more highly magnified; d transverse 

 section of a filament. 



Plate IX. 



Fig. 1. Cladophora Lyngbyei nov. sp. : a, b, c parts of the same plant; 

 a basal part with rhizoids; b more branching centre part; c 



