388 
Rhodochorton Nägeli. 
The systematical position of the genus Rhodochorton is undecided owing to the 
fact that cystocarps are unknown, and it is even uncertain whether its place is 
rightly within the Ceramiaceæ. There is much resemblance to certain species of 
Acrochetium (Chantransia’) of the family Helminthocladiaceæ, and transfers have in 
reality taken place between the two genera. Thus, Rhodochorton chantransioides has 
been transferred to the genus Chantransia by Kyrın in 1906, I have judged it ne- 
cessary to transfer Rh. seiriolanum Gibs. to the same genus (see below, p. 390), and 
I think that it may be necessary also with Rh. endophyticum Kylin (1907, p. 188) 
which has only monosporangia, no tetrasporangia. 
The cell structure usually gives good distinctive characters between the two 
genera, most of the species of Acrochetium having one chromatophore with a py- 
renoid, while Rhodochorton has several band-like chromatophores. However, as shown 
by Kuckuck (1897, p. 21), Rh. floridulum has several stellate chromatophores con- 
taining a central pyrenoid, which organ is otherwise only known within the Hel- 
minthocladiaceæ. On the other hand, the species of Acrochetium subg. Grania have 
several ribbon-shaped, more or less spiral-shaped chromatophores without pyrenoids 
in each cell. 
Antheridia have hitherto not been observed in the genus Rhodochorton. As 
mentioned below, they have now been detected in Rh. penicilliforme; these organs 
give no indication of the systematic position of the genus as they are in accordance 
with the antheridia of other Ceramiaceæ and of Acrochætium as well. The discovery 
of the antheridia raises the hope that cystocarps may also be found. 
The sporangia are always first divided by a transversal wall and afterwards 
by two vertical ones. The same mode of division occurs in Acrochetium and in Anti- 
thamnion as well. 
1. Rhodochorton penicilliforme (Kjellm.) K. Rosenv. 
L. Kolderup Rosenvinge, Les Algues marines du Groenland. Ann. d. sc. nat. Bot. 7° série tome 19, 1894, 
p- 66; id., Deuxième Mém. Alg. mar. Groenl. 1898, p. 23; F. Borgesen, Mar. Alg. Fer. 1902, p. 389. 
Thamnidium mesocarpum f. penicilliformis Kjellman, Spetsb. Thallof. I, Bih. K. Sv. Vet. Akad. Handl. 
Bd. 3 No. 7, 1875, p. 30. 
Rhodochorton mesocarpum f. penicilliformis Kjellman, N. Isl. Algfl., 1883, p. 235 (Alg. Arct. Sea p. 187), 
tab. 16 figs. 6—7; Kolderup Rosenvinge, Gronlands Havalger, 1893, p. 792. 
The species is easily recognisable by its basal system composed of regularly 
radiating connate. filaments; it has been figured by myself (1893, fig.9 A) and 
BORGESEN (1. c.). Transverse fusions between cells belonging to different rows were 
repeatedly observed (fig. 325). The free filaments project in dense tufts or more 
scattered. In several cases they were unbranched and sterile; they are 9—12 (—14) x 
* Though I do not see the necessity of exchanging the old name Chantransia, which has been 
autorized by long spending, with the later Acrochetium, I here follow the modern authors in using the 
latter name. 
