61 
Porphyra vulgaris Agardh, Flora 1827 II p. 642, Icones Algar. tab. 28; Harv. Phye. brit. pl. 211; Aresch. 
Alg. Scand. exs. No. 261. 
f. laciniata (Lightf.) Thur. in Le Jolis Liste p. 99. 
Ulva umbilicalis Lyngb. Hydr. p. 28; Flor. Dan. tab. 1663. 
P. laciniata Ag. Syst. Algar. p.191, Icones Algar. pl.27; Harv. Phye. Brit. pl.92; Areschoug Alg. scand. 
exs. No. 116 and No. 260. 
P. laciniata var. umbilicalis Ag. Ic. Algar. tab. 26. ; 
With regard to the limitation of the species I agree with Taurer (in Le Joris 
Liste), but I follow J. AGARpH in adopting the specific name of LINNÉ, as it is the 
oldest and besides not less significant than Lignrroor’s name laciniata. 
As to the f. linearis, the views of authors have been divergent. It was Harvey 
(Phyc. Brit. pl. 211) who first showed, from observations in nature, that it is 
only a juvenile winter-form, which later passes over into the broader form, and 
this has been confirmed later by THurer and others. J. AGAnpu regards it however 
as a distinct species, emphasizing that it occurs not only in winter but also in 
spring. Kyrın follows this author but without discussion of his view. Having 
observed this form in nature in winter and spring, I cannot but come to the same 
result as Harvey and THURET. In winter this species is abundant on the moles 
at Frederikshavn, on the inner as well as the outer side, and it occurs then mainly 
in rather narrow forms, which pass gradually and evenly into specimens which 
correspond exactly with P. linearis Grey. While the latter is said to attain only a 
length of a few inches, specimens more than 20 cm. long but less than 1 cm. broad, 
for the rest fully typical, were commonly found. The largest specimen I have col- 
lected is without the basal portion but is notwithstanding 43 cm. long with a 
breadth of only 0,8 cm. The typical specimens of f. linearis have a well developed 
stipe, rounded base and the margin a little or not undulated. In some broader 
specimens the margin becomes more undulated, the base broader and cordate 
(Plate II fig. 1—3). Such specimens agree with Kyrın’s P. hiemalis; the only diffe- 
rence between this and P. linearis seems to me to be, after Kyrın’s description, 
besides the somewhat greater dimensions, the fact, that the sporocarps form long 
narrow sori. This I have also observed in some of the specimens mentioned here 
(Plate II fig. 1), but by no means in all, and on the other hand it occurs also in 
broad specimens of P. umbilicalis (Plate I fig. 3), and therefore it cannot be used 
as a distinguishing character between the forms of this species. 
These narrow forms occur in great quantity in winter on the moles of Fre- 
derikshavn, particularly on the outer side of the outer moles, at high level, and 
also on moles and groins on the west coast of Jutland. In spring, when easterly 
winds occasion low water, this fact in connection with the increasing dryness of 
the air and the strong sun will cause these Porphyra plants to a great extent lo 
die. The individuals surviving this critical season are those growing at a rather 
low level or in places which are protected by particular conditions against drying 
up during low water. In growing older the frond of these individuals increases 
more in breadth than in length, and the same frond may then pass in development 
