2. Antithamnion Plumula (Ellis) Thuret. 
Thuret in Le Jolis, Algues mar. de Cherbourg, 1864 p. 112; R. W. Phillips 1897 p. 356, Pl. 18 Figs. 11— 
12; A. Nestler 1899, p. 1, Taf. I Figs. 1—10; Killian, Über die Entwickl. einiger Florideen. Zeitschr. 
f. Bot. 6. 1914, p. 215; B. Schussnig 1914 p.1; Kylin, 1915 p.11; id., Über die Keimung der 
Florideensporen. Arkiv f. Botanik Bd.14, No. 22, 1915, p. 15; id. 1923 p. 61. 
Conferva Plumula Ellis, Philos. Transact. Vol. 57 1, 1768 p. 424 Tab. 18. 
Callithamnion Plumula Lyngbye, 1819, p. 127; J. Agardh, 1851 p. 29; Harvey, Phyc. Brit. III 1851, PI. 
242; Kützing, Tab. phyc. Bd. 11, 1861, Taf. 83 I. 
Pterothamnion Plumula Nägeli in Nägeli u. Cramer, Pflanzenphys. Unters. 1. Heft 1855 p. 54, Taf. VI, 
Figs. 11—13, Taf. VII; Berthold 1882, p. 614, Taf. XX Figs. 1—2, Taf. XIX Fig. 11—17; id., Ver- 
theil. d. Alg. im Golf von Neapel; Mittheil. a. d. zool. Stat. zu Neapel 1882, Heft. III; Schmitz, 
Unters. üb. die Befrucht. d. Florid., Sitzber. d. k. Akad. d. Wiss. zu Berlin, 1883, p. 236, Fig. 35. 
In the Danish waters this species reaches a height of 9 cm, but usually it 
does not exceed 5cm. The fixation of the primary shoot is strengthened by free 
N 
Fig. 298. 
Antithamnion Plumula. See text. 70:1. 
rhizoids springing from the lower end of the cells of the main axes and the lower 
part of the lateral axes, while intramatrical rhizoids do not occur. It happens, how- 
ever, that several of the downward growing filaments do not reach the substratum. 
Some of them may take the character of runners which give rise to upright shoots; 
they then consist of shorter, thicker cells. Intermediate stages between assimilative 
shoots and root-like filaments, showing unstable polarity, may occur too. The long 
shoot to the right in the fig. 298, for instance, is essentially an assimilatory shoot; 
the filament issuing from its second joint is, however, a branched rhizine though 
it has been produced at the upper (distal) end of the cell. The Sth cell of the same 
shoot has also produced at its upper end a filament having if anything the char- 
— nn 
