Fam. 19. Plocamiaceæ. 
Plocamium Harv. 
1. Plocamium coccineum (Huds.) Lyngb. 
Lyngbye, Tent. 1819, p. 39, tab. 9 B; Kützing, Phycol. gen. 1843, p. 449, Taf. 64; Harvey, Phyc. Brit. I, 
pl. 44, 1846; Nägeli, Neu. Algensysteme 1847, p. 228, Taf. X, figs. 22—37; J. Agardh, Sp. g.o. Alg, 
Vol. II.2, p. 395, 1852; Kützing, Tab. phycol. Bd. 16, Taf. 41; Schmitz, Untersuch. 1883, p. 26, 
Taf. V, figs. 37—38; Buffham 1884, p. 338, 1891 p. 249, Plate 16, figs. 8—9; Phillips, Developm. of 
the cystocarp in Rhodymeniales, Ann. of Bot. 11, 1897, p. 352; Oltmanns, Morph. u. Biol. 1904, 
pp. 597, 646, 661; Kylin 1923, pp. 49—53. 
Fucus coccineus Hudson, Flora Anglica. Tom. II, 1778, p. 586, Goodenough and Woodward, Transact, 
Lin. Soc. 1797, III, p. 187. 
The structure of this common Atlantic species has been described by KüTzING 
(1843), NÄGELT 1847, OLTMANNS (1904) and Kyrın (1923). The ramification and 
the cell-divisions at the tips of the frond were 
carefully explained by NAGEL1 who stated that “> 
in the vegetative pinnæ the apical cell is first + 
divided by transverse walls, whereas they XV 
“beendigen ihr Wachsthum meist durch shiefe A 
Wände’...“DieSporenäste und Keimäste dagegen | 
wachsen durch schiefe Wände in der Scheitel- Fig. 602. 
zelle” (1. Cc. p. 228). KYLIN says (1923, p- 51) N re re 
that he has not observed the oblique divisions 
of the apical cells, and it must be admitted that the apical cell of most of the 
vegetative pinnulæ are divided only by transverse walls. NAGELI’s statement is, 
however, correct, at least for the feebler vegetative and for the male pinnule. In 
the lowermost, feeblest pinnula in a row, the last dividing walls of the apical cell 
are oblique, alternating (fig. 602), whereas the upper pinnulæ are divided by trans- 
verse walls to the very end of their growing activity, and in the tetrasporiferous 
pinnule the apical cells early begin to divide by oblique walls; the lateral ones 
are even divided only in this manner (fig. 603). In a female plant with young 
procarps, I found only transverse divisions in the apical cell of the pinnule. 
As to the anatomical structure and its development reference may be made 
to the quoted paper of Kyrın. We shall merely emphasize that the frond contains 
a central row of long cells rich in protoplasm, and is built up of an inner tissue 
of large parenchymatous cells which can be designated as a storage tissue, as it is 
rich in starch grains, and an outermost layer of small cells, which is essentially 
an assimilatory tissue; its cells contain numerous small chromatophores. Hyaline 
hairs are not produced. 
Antheridia were not observed in the Danish specimens. According to BUFFHAM 
(1891) and Kyrın (1923, p. 53) they form a layer on the surface of the pinnule of 
the last and penultimate order. 
