61 



I'orpluiia niilgaris Agardli, Flora 1827 II p. (U2, Iconcs Algar. tab. 2«; llarv, I'iiyc. hrit. 1)1.211; Arcscli. 

 Alg. Seand. exs. No. 2G1. 



r. laciniuta (Lightf.) Thur. in Le Jolis Liste p. 99. 



Ulua uinbilicalis Lyngb. Hydr. p. 28; Flor. Dan. tab. I(3(i3. 



P. luciniata Ag. Syst. Algar. p. 191, Icoiies Algar. pl.27; Harv. Phyc. Brit, pl.ll^'; Arcschoug Alg. scand. 



exs. No. 116 and No. 260. 

 P. laciniata var. uinbilicalis Ag. Ic. Algar. tab. 26. 



With regard to the Hmitation of the species I agree with Thuret (in Le Jolis 

 Liste), but I follow J. Agahdh in adopting the specific name of Linne , as it is the 

 oldest and besides not less significant than Lightfoot's name laciniata. 



As to the f. linearis, the views of authors have been divergent. It was Hauvey 

 (Phyc. Brit. pi. 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 Thuret and others. J. Agardh regards it however 

 as a distinct species, emphasizing that it occurs not only in winter but also in 

 spring. Kylin 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 Grev. 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 Kylin's P. hienialis\ the only diffe- 

 rence between this and P. linearis seems to me to be, after Kylin'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. amhilicalis (Plate 1 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 to 

 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 



