370 
slender and often longer than in A. Plumula. Gland-cells (fig. 307) similar to those 
of À. Plumula may be present or wanting. They were present in all the examined 
specimens from the eastern Kattegat and further in some of the specimens from the 
Samsø waters, though in some cases only in small number, while they were wanting 
in other specimens, and they were also wanting in all the examined specimens 
from the Øresund and from the Baltic Sea. The latter specimens can be referred to 
f. baltica Reinke (1. c.) which is chiefly distinct by this character. The specimen re- 
presented by Kuckuck in Atlas deutsch. Meeresalg. Taf. 22 has in great part unbranched 
pinnulæ, which occurs more rarely in the 
specimens from the Danish waters. 
The tetrasporangia are sessile on the 
upper face of the pinnulæ or on their 
flanks, usually singly on the joints but 
sometimes in pairs and the second being 
inserted at a lower level but at the same 
time beside the first. The sporangia are 
bigger than in A. Plumula, usually 60— 
85 w long, 35—50 w broad. In the specimens 
from Feng Sund, however, I found them 
a little smaller, only 46—49 w long, 35 u 
broad, thus almost of the same size as 
those in A. Plumula. 
In some specimens from the Little Belt 
and the Baltic Sea antheridia were met 
Be u with. They were borne on the upper end 
Antithamnion boreale. Pinnulæ bearing antheridia at 5 i å 
the top, and sporangia, s. g gland cells. In Athe*chrom. Of short pinnulæ which in several cases 
atophores are shown. A—C 390:1. D 230:1. bore sporangia too (figs. 306, 307). These 
pinnulæ usually consist of 3—6 cells the 
uppermost one or two of which bear a small number of closely placed nearly glob- 
ular antheridia. The pinnula may sometimes bear a small branch which likewise 
bears antheridia at its top (fig. 306 above), but antheridial clusters like those in A. 
Plumula never occur. 
Female sexual organs and cystocarps have never been observed in this species. 
The presence of antheridia-bearing pinnulæ in tetraspore-bearing specimens 
and the different shape of these branchlets corroborate the view that A. boreale is 
specifically distinct from A. Plumula. As stated by previous authors, A. boreale is 
nearly related to A. americanum (Callithamnion americanum Harvey, Nereis bor. 
amer. II, 1853 p. 238 pl. 36 A). In a specimen of this communicated in Phykotheka 
univers. No. 501 I found gland-cells and sporangia 56—60 w long, 35—37 w broad. 
A. boreale occurs in the Danish waters almost exclusively south of Anholt, in 7 
to 40 meters depths, most frequently in 13 to 30 meters depths. The innermost local- 
ities known are Davids Banke north of Bornholm and a place east of Bornholm 
