459 
Odonthalia Lyngbye. 
1. Odonthalia dentata (L.) Lyngbye. 
Lyngbye Hydr. 1819, p. 9 tab. 3 A; Orsted De reg. mar. 1844 p. 52; Harvey Phye. brit. I 1846 PI. 34; 
J. Agardh, 1863, p. 899; Wille, 1885, pp. 30, 50, Tab. IV figs. 48—49; id. 1887, p. 69 figs. 32—37; 
Buffham 1893, p. 297, Pl. XIV figs. 33—36; Falkenberg 1901, p. 604, Taf. X figs. 6—22. 
Fucus dentatus Lin. Syst. nat. ed. 12, vol. II, p. 718. 
Fucus pinnatifidus Oeder Fl. Dan. Tab. 354, 1767. 
Rhodomela dentata Lyngb., Rar. cod. 1880 p. 225. 
The morphology of this species shall only be mentioned here rather shortly 
as it has been treated at length by FALKENBERG (1901). As mentioned by this author, 
p. 605, the two-edged shape of the frond is caused partly by the formation of a 
wing on each side of the frond, partly by the congenital coalescence of the lower 
parts of the shoots The branch-bearing segments are, in the sterile parts of the 
frond, separated by 2—4 segments bearing no branch (fig. 422). The ectoblastesis 
(L. K. R. 1920 p. 20) is very prominent. As emphasised by FALKENBERG, there are 
no trichoblasts. The pericentral cells divide early and thus become covered by a 
layer of smaller cells which divide further and the outermost of which are so arranged 
that four transversal rows correspond to the height of a primary segment (comp. 
FALKENBERG p. 606, our fig. 422 B). It deserves further notice that triangular initial 
cells are to be found in the edge of the frond, in particular where the outline is 
convex, one for each secondary segment (fig. 422 B). There is thus resemblance with 
the edge of Delesseria. but with the difference that the initial cell is seated in the 
lower (basiscopic) corner of the segment while in Delesseria it is to be found in 
the upper corner. In Apoglossum ruscifolium, however, I also found marginal initial 
cells with the same orientation as in Odonthalia (comp. p. 459). FALKENBERG has 
delineated these initial cells in 
Odonthalia (1. c. Pl. 10 Fig. 12), 
but he has not shown the pro- 
duces of their divisions. 
The frond of the last year 
has a slightly projecting mid-rib 
which contains the central cell 
in the centre. This cell is com- 
paratively narrow but becomes 
very long and is connected with 
the contiguous central cells 
through a large primary pit; it 
contains several nuclei but pro- 
duces no starch. The other cells 
of the inner tissue have a larger 
Fig. 422. 
. Odonthalia dentata. Tips of growing plant. J—III the successive 
diameter (fig. 423 A) but are generations of branches. 350 :1. 
