359 
The three kinds of organs of reproduction (antheridia, procarps and tetraspo- 
rangia) normally occur on distinct individuals. BurrHam, however, (1896, p. 189) 
found tetrasporangia on female plants. In one case “the involucre of an old cysto- 
carp (or possibly of an unfecundated procarp) became branched near the tips and 
developed tetrasporangia”. 
The species occurs in the Skagerak, where it has been collected at 11—15 
meters depth, in the eastern and southern Kattegat in the under-current with high 
salinity, in about 20—30 meters depth and in the northern part of the Sound in 
the same current. It most frequently grows on the stipes of Laminaria hyperborea 
and L. digitata. It is perennial but has only been collected in the months May to 
October. It reaches a size of 15 cm. In specimens gathered in June the new shoots 
had a more clear red colour than the older parts of the frond which were more 
brown-red. The new shoots in great part formed a continuation of the old ones, 
but adventitious shoots also occurred, arising from the base of the pinnulæ, as de- 
scribed and figured by Cramer (1. c.). In August the vegetative growth has ceased. 
Antheridia were met with in May, unfertilized carpogonia in June, and ripe cysto- 
carps and tetrasporangia in June to September. 
Localities. Sk: Off Hirshals, 12 m (Borgesen); XO, Mollegrund off Hirshals, 11—15 m. — Ke: 
IQ, ZF and fH, Fladen, 17—30 m; 4'/2 miles S.W.°/ı W. of Fladens light-ship, 30 m (C. A. J.). — Ks: 
Lysegrund, June 1832 (Lyngbye); Nordvestrev by Hesselo, July 1832 (Lyngbye). — Su: Gnetare Grund 
and Grolle Grund at the shore of Sweden (Boye Petersen); off Hellebæk, soft bottom with shells (id.); 
north of Helsingør (Liebman, Ørsted). 
Antithamnion Nageli. 
1. Antithamnion cruciatum (Agardh) Nägeli. 
C. Nageli, 1847, p. 200, id., 1861, p. 378; J. Reinke, Lehrbuch d. allgem. Botanik, 1880, p. 171 Fig. 121; 
G. Berthold, 1882, pp. 573, 605, Pl. 19 Figs. 1—10, Pl. 20 Figs. 3—4; P. Kuckuck, Bemerk. z. mar. 
Algveg. Helgoland, Wiss. Meeresunt. Abt. Helgoland N. F. Bd. 1, 1894, p. 254 Fig. 22; Nestler 1899, 
p- 5, Taf. I Figs. 11—19; B. Schussnig, 1914 p. 2. 
Callithamnion eruciatum C. Agardh, Flora 1827 II, p. 637; Harvey, Phye. Brit. II 1849, p. 164; J. Agardh, 
1851, p. 27; Kützing, Tab. phyc. Vol. 11, 1861 Taf, 87 I; J. Agardh, Florideernes Morfologi, 1879 
(K. Sy. Vet. Akad. Handl. Bd. 15 No. 6), p. 103 PI. I Fig. 20 (Cystocarp). 
&, genuina. | 
8, radicans J. Agardh, Symbolae, Linnaea, 1841, p. 44. 
This species is easily distinguishable from the two following species. Each joint 
in the long shoots bears two opposite or four verticillate pinnæ. In the Danish 
specimens I found them only opposite; they were decussate, and thus arranged in 
four rows. The angle of divergence often diverged from 90° and was variable, and the 
arrangement in longitudinal rows therefore not distinct. As shown by BERTHOLD 
(1882, p. 605), the position of the pinnæ is dependent on the light, the pinnæ being 
inclined to place themselves in a plane perpendicular to the incident light. According 
to NAGEL (1861, p. 379) the pinnæ in the whorls do not arise simultaneously and 
the first pinnæ of the successive whorls are arranged in a spiral with the divergence 
46* 
