318 
resemblance to C. fruticulosum. Kyıın (1907, pp. 154—162) points out the accordance 
in the morphological structure existing between these three forms which he considers 
as distinct species, and he further describes a new, fourth species, C. spiniferum 
characterized principally by thinner pinnulæ, 25—40 w thick, and consisting of longer 
cells, 5—8 times as long as broad, while in C. fruticulosum the pinnulæ, according 
to Kyrın, are 40—60 x thick and consist of cells 3—5 times as long as broad. 
I cannot acknowledge the right of distinguishing these four forms as species, 
at all events not with the delimitation given by Kyrın. The specimens found at the 
Fig. 231. 
Callithamnion tetragonum var. divaricata. A, pinna. B, branch-system with tetrasporangia. C, branch with tetra- 
sporangia and an arrested procarp p. A, B 70:1. C 200:1. 
North coast of Sealand agree perfectly with J. AGARDH’s description of C. fruticulosum 
and with specimens from AcarpH (from Kullaberg), and the dimensions of the cells 
in the pinnulæ correspond also with those attributed to this species by Kyrın, viz. 
3—5,5 times as long as broad; but the thickness of the pinnule is the same as that 
attributed to C. spiniferum, viz. 23—42 u. In specimens found in the Northern Katte- 
gat, the pinnulæ are thicker and of a structure more resembling that of C. brachia- 
tum, but in some of the specimens the pinnule were up to 123 w thick and consisted 
of cells only 1,2—2,7 times as long as broad, thus resembling those of the typi- 
cal C. tetragonum; the cells were, however, not barrel-shaped and the pinnulæ 
were thickest at the base. My investigations have led me to consider all these sup- 
posed species as forms of one species which must bear the name of the first described 
