309 
1. Callithamnion Hookeri (Dillw.) Agardh. 
C. Agardh, 1828, p. 178; Harvey, Manual Brit. Alg. 1841, p. 106; J. Areschoug, 1850, p. 103, tab. IV F 
(forma a); J. Agardh, 1851, p. 51; Harvey, Phyc. Brit. Vol. III, 1851, pl. 279; Kützing, Tab. phycol. 
XI tab. 94a, 1861; Kylin, 1907, p. 150. 
f. Areschougü nob. 
Areschoug, I. c. forma a, Alg. scand. exsice. No. 311; Kylin, 1. c. f. {ypica. 
Callithamnion pyramidatum Liebman, Bemærkn. o. Tillæg, Kroyers Tidsskrift II, 1839, p. 479, Tab. VI 
fig. 1, ex parte. 
In several places in the Danish waters a Callithamnion has been met with 
which agrees exactly with Callithamnion Hookeri a Aresch., as described by ARE- 
Fig. 216. Fig. 217. 
Callithamnion Hookeri. Upper end of sterile shoots. Callithamnion Hookeri. After a living 
A 150:1. B 70:1. plant. 160:1. 
SCHOUG and Kyrın, Il. cc., and bearing, like the Swedish plants, heaps of paraspores 
but no or scarce tetrasporangia and never sexual organs. The Scandinavian specimens 
have certainly justly been referred to C. Hookeri Harvey; but as they differ from the 
British specimens by the presence of paraspores and by the absence of sexual or- 
gans they might be regarded as representing a particular form of the species. 
The Danish specimens ordinarily reach only a length of 1,5—2 cm; but they may 
become up to 3cm high (Skærbæk). The stem and the main branches are very 
distinct, not bent in zigzag, covered with down-growing cortical filaments. The rami- 
fication is mainly pinnate, the consecutive cells bearing each a branch alternating 
with the foregoing. Vigorous branches generally show a pinnate ramification, the 
pinnulæ lying all in the same plane, and being rather diverging. The lateral branches 
do not generally reach the level of the top of the main axis, and the outline of the 
shoot is therefore lanceolate, pointed above (comp. fig. 216). Exceptions may how- 
D. K. D. Vidensk. Selsk, Skr., 7. Række, naturvidensk. og mathem. Afd., VII. 3. 40 
