371 
where only very small specimens were met with which were much reduced, many 
of the joints bearing only one branchlet. The specimens from the Kattegat were up 
to 5 cm high while those from the southern waters reached only a length of 2,5 cm. 
It usually grows on other Algæ e. g. Delesseria sinuosa, Furcellaria fastigiata and Co- 
rallina offinalis and on Hydroids. It has been met with in the months April to 
August and bore sporangia in the same months. Antheridia were met with in May 
and June. — In the western part of the Baltic Sea it has been found by REINKE 
in four localities, at the west coast of Sweden it has not been found north of La- 
holms Bugt (Kyrın). 
Localities. Kn: Harbour of Frederikshavn. — Ke: ER, Fyrbanken, east of Anholt, 28 meters. 
— Ks: EO, north of Lysegrund, 26 m. — Sa: PJ, Ebeltoft Vig, 13 m; PL, Wulffs Flak; DK, Bolsaxen, 
14 m. — Lb: Fæno Sund, 15 m; dQ, bank south of Lyø, 22 m; dH’, east of Hesteskoen, 18—19 m. — 
Sb: DL, south of Refsnæs, 7 m; cN, south-west of Musholm, 18 m; cL, north-east of Sprogø, 25—27 m; 
Z, off Skagbo Huse, 19 m; UH and UT, Langelandsbelt, 19—22 m; US, Langelandsbelt, c. 40 m; US}, 
near the former, 20 m. — Su: Off Aalsgaarde, shelly bottom (Boye Petersen); north of Lappegrund, 
19—26 m (Henn. Petersen); bM, south of Hveen, 23 m. — Bw: Trindelen, west side of Kegnæs, Als; 
UL, Øjet, 20 m. — Bb: SN, Davids Banke, 15—17 m; 3 miles S.S.E. of Nexo, 21 m (C. A. J.). 
Maenus (Bot. Erg. Nordseefahrt p. 67) has reported Callithamnion Plumula Lyngb. from “N.W. 
von Roesnäs 28 Faden” and “N.W. von Fænû 16—10 Faden”. Without examining the specimens in 
question it is impossible to decide whether they must be referred to A. Plumula or A. boreale. 
Ceramium (Roth) Lyngbye. 
In 1908 Dr. HENNING PETERSEN published a monograph on the Danish 
species of the genus Ceramium, based principally on the material contained in my 
collections, and in a later paper (1911) he has again mentioned some of the species. 
Since the publication of these papers I have made further collections of Ceramia 
in the Danish waters, and Dr. PETERSEN has then readily complied with my request 
to examine these new collections together with his own later gatherings, and he 
has at the same time made a revision of his earlier determinations. These investig- 
ations have in several cases led Dr. PETERSEN to another limitation of the species, 
and as the new collections have brought species to light which were formerly not 
known from the Danish coasts, the number of Danish species has been increased 
from 10 to 18. Dr. PETERSEN has communicated to me descriptions and remarks on 
several of the species, which are given below, partly with Dr. PETERSEN’s own words. 
further some drawings and a new key to the species, while I contribute the account 
of the occurrence and fructification of the species and give some drawings and a 
few general remarks on the morphology. 
The vegetative morphology and development has been treated by Cramer (1863). 
The germination has been repeatedly studied by various authors, (comp. KYLIN 
1917, where further literature is quoted). I have examined the germination of the 
tetraspores of C. rubrum and of the paraspores of C. strictum which take place in 
essentially the same manner, but I have nothing to add to the earlier descriptions. 
