386 
17. Ceramium septentrionale Henn. Petersen. 
Henn. Petersen 1911 p. 110, figs. II—IV.' 
C. circinnatum Kützing f. borealis Foslie, The norweg. forms of Ceramium. D. 
kgl. norske Vidensk. Selsk. Skrifter 1893, Trondhjem 1894 p. 9. 
Having examined Fostte’s original specimens of the above named form I must 
consider this form as belonging to C. septentrionale described by me in 1911. It 
differs much from C. circinnatum which is characterised by downward growing zones. 
C. septentrionale is characterised by very high cortical bands, often reaching a height 
of 1—2 mm. (HENN. PETERSEN). 
The Danish specimens referred to this species are all older specimens reaching 
a length of 13 cm, collected in July and August, with tetrasporangia and cystocarps. 
The tetrasporangia are cruciately divided. A specimen still in growth, with cystocarps, 
collected by A. OTTERSTROM off Frederikshavn in Aug. 1902, formerly referred to 
C. fruticulosum f. dichotoma and represented under this name in Ceram. Stud. 1911 
pl. I fig. 1 is now referred with some doubt by Dr. PETERSEN to C. rescissum Kylin. 
Localities. Kn: Near Hjellen 6—7 m (H. E. P.), Københavner Rev (Boye Petersen) and Borre- 
bjergs Rev (H. E. P.) near Frederikshavn. 
18. Ceramium rubrum (Huds.) Agardh. 
Henning Petersen 1908 pp- 73 and 93, Plate IV Figs. 5, 6, Plates V—VII: id. 1911 p.113, Plates III, IV, 
V Figs. 25, 27—30. 
Whereas in 1908 I referred certain forms with partly separate cortical bands 
to this species, I now judge it better to exclude such forms. Distinct bands have 
been met with in certain forms from deeper water, which in 1908 were named f. 
decurrentoides, and further in f. irregularis subf. subcorticata. As to the latter I am at 
present in doubt but I hope to contribute later to the question of its systematical 
position. On the other hand I do not doubt that f. decurrentoides cannot be referred 
to C. rubrum, and I have therefore described it as a new species, C. abyssale (p. 384). 
As a new form is distinguished f. furcata which seems to be a f. irregularis 
developed from f. prolifera; it has a similar occurrence to this. It is characterised 
by robust branches and often straight apices with long forcipes. In certain cases it 
resembles C. rubrum f. linearis H. Ptrsn. 1911, p. 116 fig. VI, pl. IV fig. 21. 
Another form new in the Danish flora is f. fasciculata. HENN. PETERSEN. 
The numerous forms occurring in the Danish waters of this widely spread 
species have been treated at length by Dr. PETERSEN (1908 pp. 73 et seq.). All 
the forms now distinguished by this author are named below. 
The forms prolifera, secundata and pedicellata (virgata) have only been met with from 
Ns and SK except f. prolifera, which has also been found in the Limfjord (N. side of Fur). 
* In Cer. Stud. 1911, the pl. V fig. 26 is given as representing C. septentrionale, but this is er- 
roneous; the figure in question represents either a new species or a particular form of C. rubrum (H. Ptrsn.) 
