188 KJELLMAN, THE ALGH OF THE ARCTIC SEA. 
Habitat. Only a few specimens have been found within the sublitoral zone, 
attached to Chawtomorpha 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 (Kttz.) Tuur. 
in Le Jol. Liste Alg. Cherb. p. 16; Kurz. Phye. 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 cireumnatans, fronde usque 90 em. longa, 
30 cm. lata, ovata, ovato-cordata, oblongo-obovata, oblongo-lanceolata, crebre et profunde undulato-plicata, non 
lobata, juvenili intense violaceo-purpurea, ztate provectiore plus minus dilute violaceo-carnea, lubrica, charte 
aretissime adherente; cellulis medii thalli planta adulte 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 Kueen, Nord]. Alg. p. 23. 
» coccinea Kieren, Nordl. Alg. p. 24. 
Ulva umbilicalis 6 purpurea We. Fl. Lapp. p. 506. 
Description of the species. This alga is at first attached to other alge 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 reseinbling 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 this figure as well as the others are drawn from dried and 
