376 
1. Ceramium tenuissimum (Lyngb.) J. Agardh. 
Agardh, 1851, p. 120: Henn. Petersen 1908, pp. 54, 49 pl. I Fig. 1, 190, p. 97; idem 1911, p. 97. 
i 
C. diaphanum var. tenuissima Lyngbye Tent. p. 120. 
As shown by Henn. PETERSEN, the species is easily distinguished by the dent- 
iculate outline of the young incurved branches, by the presence of gland cells and 
by the extruding tetrasporangia usually single in the cortical zones. It reaches a 
length of 8—10 cm: in the Little Belt and the South Fyn Waters, however, spec- 
imens higher than 3 cm were not met with. It occurs in all seasons; in winter, 
however, it is only 1—2 cm high. It is spread 
in all the Danish waters from the Skagerak to 
the south Fyn waters, but has not been met 
with in the Great Belt, the Sound and the 
Baltic Sea; it thrives well in the fjords (Lim- 
fjord, Isefjord, Odensefjord). It occurs from a 
little under low-water mark downwards; in the 
eastern Kattegat it has been met with in 22,5 m 
depth. It has been found with tetrasporangia 
in July and August, with cystocarps in July 
and September. Antheridia were met with in 
July 1923; they covered the surfaces of the 
joints in longer stretches of the frond. Epiphytic 
on various Alge and on Zostera. 
Fig. 314. 
Ceramium ienuissimum. A. upper end of filament Localities. Sk: YN®, E. of Bragerne; SY, N. of 
with hairs, partly decayed. B, band with tetra- Lokken, 13 m; XO off Hirshals; Hirshals mole (Børgesen) 
SED LSU eb 5 EURE and near land. — Lf: Nissum Bredning; ZS, ZY; Thisted 
Bredning: MH; Sallingsund: Nykøbing; Løgstør Bredning: 
LS, 7 m, bT; off Feggeklit, 4m. — Kn: Off Hulsig, 8 m (B. Petersen); N.E. of Hirsholm (Ostenfeld); 
TP, Tønneberg Banke, 16 m; Brune Rev by Frederikshavn (H. E. P.); ZP, UC, N. of Nordre Rønner. 
— Ke: Fladen: ZG, ZF, VY. 18—22,5 m: Gilleleje (Lyngbye). — Km: Læsø Rende: Dana St. 2919 
(C. A. J.); BO off Stensnæs; ZC* within Kobbergrund; VL south of Tangen; BH off Gjerrild Klint. — 
Ks: Isefjord: EH off Lynæs, near Rørvig (Joh. Lange), Lammefjord. — Sa: Reef by Kalø; BB, Søby 
Rev: Korshavn, reef; Odensefjord, Hofmansgave (Lyngbye, C. Rosenberg). — Lh: Helnæs Hoved Flak; 
CC, Hornenæs. — Sf: Shoals off Nakkebølle Fjord. 
2. Ceramium diaphanum Harv. et J. Agardh. 
Henn. Petersen 1908 pp. 56, 87 figs. I,1, II and IV,1,4, pl. I figs. 2—5, pl. IL figs. 3—4, 1911 p. 98, 
fig. 1,1, 4, pl. I fig. 2. 
This species is common in the inner Danish waters where it usually grows 
near the low-water mark on piers in harbours and in stony reefs in about one 
meter's depth, more rarely descending to 4—5 meters depth or even to 13 m. It 
grows on stones and wood, Chorda Filum, Zostera, Fucus vesiculosus a. o. Algæ. It 
reaches a length of Scm. It has been met with from April to November but is 
