320 
these are more divaricate than in that variety. The pinnulæ have their greatest 
thickness at the base and gradually taper upwards. Their greatest thickness is 
somewhat variable; it was greatest in a specimen met with in November in 
Busserey at Frederikshavn, viz. 50—124 u, frequently over 100 w. In small specimens 
found in the same locality in July it was only 49—63 w. The length of the cells 
was in the first case 1,25—2,7, in the latter case 2,5—3 times the breadth, and 
similar dimensions of the pinnulæ were found in specimens from Marens Rev (Ja- 
nuary) and Hirsholmene (July). In the pinnæ with arrested growth, the last pinnulæ 
were more or less divaricate (figs. 231—232). 
The tetrasporangia are placed on the inner side of the pinnæ, usually beside 
and at a lower level than the branches. Tetrasporiferous pinnæ with arrested growth 
may form corymbiform clusters. The sporangia are nearly globular, 62—70 w long, 
51—59 u broad. In sporangiferous specimens, undeveloped procarps may be found 
in the same pinnæ as the sporangia (fig. 231 C). 
Found with ripe tetrasporangia in July and November, with ripe cystocarps 
in July. 
Localities. Nordostrev by Hirsholm, in Furcellaria, 7,5—9,5 m; Busserev and Marens Rev by 
Frederikshavn. 
ar. fruticulosa J. Agardh. 
Kolderup Rosenvinge 1920, p. 7. 
Callithamnion fruticulosum J. Agardh, Symbolæ, Linnæa, 15. Bd. 1841, p. 46, Spec. gen. ord. Alg. II p. 56, 
1851; Kylin, Algenfl., 1907, p. 154. Non Roth, Catalecta II, 1800, p. 183, nec Lyngbye, Hydr., 
1819, p. 124. 
Callithamnion Hookeri (Dillw.) b. Areschoug, Phyc. scand. 1850, p. 104. 
Phlebothamnion fruticulosum Kützing, Tab. Phyc. 11, 1850, pl. 95. 
Callithamnion Baileyi Harv., Ner. Bor. Amer. II. 1853, p. 231, pl. 35 B; Färlow Mar. Alg, N. Engl., 1881, 
p- 127, pl. XI, figs. 1—2. 
Phlebothamnion Baileyi (Harv.) Kützing, Tab. phyc. 11, 1850, pl. 95. 
Callithamnion spiniferum Kylin, 1. c. p. 159. 
When J. AGARDH has named this plant C. fruticulosum, it might be. observed 
that it is not identical with the plants which have formerly been designated by 
this name. J. AGARDH has himself identified Rorn’s species with C. versicolor Draparn., 
and C. fruticulosum Lyngbye is at all events also a different species. I do not doubt 
that our plant is identical with C. Baileyi or with one of the forms of this variable 
species of which Harvey declares, 1. c. p. 232 that “the most robust forms, with 
shortest joints, approach inconveniently near to C. tetragonum, from which species 
the more delicate ones appear widely different.” In North American specimens from 
FarLtow and SAUNDERS I found cystocarps and antheridial-cushions resembling those 
in the European species. 
As mentioned above, I cannot regard C. spiniferum as a species distinct from 
C. fruticulosum, the dimensions of the pinnulæ offering no distinctive characters. 
According to Kyrın (I. c. pp. 157—162), the dimensions of the gonimoblasts and the 
