188 KJELLMAN, THE ALG^ OF THE ARCTIC SEA. 



Habitat. Only a few specimens have been found within the sublitoral zone, 

 attached to Chcetomorpha melagonium in August. They bore plenty of tetraspores. 



Locality: Known only from the Greenland Sea at Fairhaven on the north-west 

 coast of Spitzbergen. 



Fam. PORPHYRACE^ (Kutz.) Thdb. 



in Le Jol. Liste Alg. Cherb. p. 16; KiJTZ. Phyc. gener. p. 382; char. mut. 



Gen. Diploderma nob. 



Thallus membranaceus duobus cellularum stratis constructus. 



Diploderma amplissimum nob. 



Planta initio aliis algis adnata, demum soluta in mari libera circumnatans, fronde usque 90 cm. longa, 

 30 cm. lata, ovata, ovato-cordata, oblongo-obovata, oblongo-lanoeolata, crebre et profunde undulato-plicata, non 

 lobata, juvenili intense violaceo-purpurea, aetate provectiore plus minus dilute violaceo-carnea, lubrica, charlae 

 arctissime adhserente; cellulis medii thalli plantse adultse sectione transversali quadratis vel verticaliter rectangu- 

 laribus; organis reproductionis zonam marginalem subflavam occupantibus. Tab. 17. fig. 1 — 3; tab. 18, fig. 1 — 8. 

 Syn. Porphyra laciniata f. linearis et vulgaris Kleen, Nordl. Alg. p. 23. 

 » coccinea Kleen, Nordl. Alg. p. 24. 



Ulva umbilicalis /? purpurea Wa. Fl. Lapp. p. 506. 



Description of the species. This alga is at first attached to other algae by means 

 of a feeble holdfast. At this time it has a strong, saturated, purplish-violet colour. After 

 having attained a more considerable size, it is loosened and floats about on the surface of 

 the water. In proportion as it grows larger and older, it bleaches more and more, passing 

 finally to a livid, flesh-colour inclining to violet. The largest specimen I have found 

 attached was 28 cm. long by 12 cm. broad at its broadest place. Drifting individuals 

 reach a considerable size. I have measured one that was 90 cm. in length by 30 cm. 

 in breadth. The shape of the frond is subject to great variation, but in general it is 

 oblong, inclining to cordiform or ovate. It sometimes bends round the fastening-point 

 by developing one side more strongly, so as to get, when this bent is at its strongest, 

 an appearance resembling that of Porphyra laciniata f. umbicalis. It is densely folded, 

 often so deeply that the folds extend to the middle line of the frond. The margin is 

 either even or irregularly laciniate, sometimes, though rarely, beautifully crenulated. I 

 have not seen any lobed specimens; tab. 17 fig. 1 — 3. The stipital portion of the 

 frond is composed of claviform cells with the shafts directed downward and more or 

 less obliquely outward, shooting beyond one another (tab. 18, fig. 1, 2). In fully de- 

 veloped individuals the cells at the middle of the frond, in cross section, are generally 

 squarish, sometimes rectangular, considerably more high than long. I cannot determine 

 at present whether this difference denotes different ages or different forms. The shape 

 and disposition of the cells as seen from the surface, is shown in fig. 3. It should be 

 remarked, however, that tliis figure as well as the others are drawn from dried and 



