112 
The above diagnosis is made after specimens growing on Porphyra umbilicalis 
in the harbours of Skagen and Frederikshavn. They are somewhat more branched 
than f. luxurians and have a little thinner filaments and shorter cells. The spor- 
angia are very numerous and, at least in many specimens, all tetrasporous. They 
are in a great measure placed on branchlets which are usually opposite, partly 
also sessile on the sides of the filaments. From the characters mentioned this 
form is, in spite of its great resemblance, so different from the main form, that I 
was for some time inclined to regard it as a 
distinet species, but some other less pronoun- 
ced specimens have led me to the result that 
it is closely related to the f. luxurians and 
still more to the f. secundata. Thus I found 
at Middelfart some specimens having chiefly 
monosporangia, 16—20 „ long, 11—13 » broad, 
but also some tetrasporangia, and the spor- 
angia were placed on the filaments as well 
as on the branchlets. These specimens might 
be regarded as intermediate between f. lua- 
urians and f. tetrica, but they were also re- 
lated to f. secundata, differing however by 
longer cells (8—5 diameters long). The re- 
semblance between the f. fetrica and f. secun- 
data will be seen on comparing fig. 38 with 
fig. 39. To this form at least some of the 
Færoese specimens mentioned by BORGESEN 
(1. c. fig. 53) may be referred. 
Only found in summer, the typical spec- 
imens growing on Porphyra umbilicalis. 
Localities. Kn: Harbours of Skagen and Frede- 
rikshavn. — Sa: Middelfart, on Cladophora. 
— UI 
ba 5 x 
Cs, 5 AD) \\ 7, secundata (Lyngb.). 
== . Callithamnion Dawiesii 5, secundatum Lyngb. Hydr. 
Be, p.129 tab. 41. 
Chantransia virgatula 7, secundata. Plants growing 2 3 a 
on Porphyra umbilicalis at Esbjerg. A and B, bran- Acrochetium secundatum Neg. Beitr. Ceram. p. 405. 
ched filaments with monosporangia. Cand D, young Chantransia secundala Thur. in Le Jol. Liste p. 106; 
plants. 260: 1. BORGESEN, M. A. Fer. p. 350; Kuckuck in OLTMANNS, 
Morph. Alg. I p. 650; Kyrın (1907) p. 115. 
That Ch. virgatula and Ch. secundata are nearly related and often difficult to 
distinguish from each other has often been admitted, also by BorGESEN and Kuckuck, 
who think however that for the present they ought be kept distinct (BORGESEN I. c. 
p.354). I have also wished to regard Ch. secundata as a distinct species, but I have 
ended by referring it as a form to Ch. virgatula, as the limit between them, accor- 
ding to my experience, cannot be drawn without arbitrariness. As mentioned above, 
