Iioni r. linearis llirouyh I', inilyaris lo 1". laciniata (fonii). Thukkt in I^i-; .loi.is Lisle 

 [). 100). In r. inilgaris liie longiludinal axis of Ihe IVond is muc'li longer than Ihe 

 radii going onlwards or downwards, but under the continued growth of the frond 

 in transverse direction this difference diminislies and al last entirely disappears, 

 the frond obtaining an approximately orbicular outline, at the same time becoming 

 more or less laciniated and, on account of the continuous transverse growth, much 

 ladially folded (Plate I fig. 2). The point of attachment in this stage is only appa- 

 rently, not really central and umbilicate, as supposed in the older descrii)tions and 

 drawings (Linne, Spec, plant. II 1703, and Dillkmi s. Hist, nuiscor. 1741. tab. 8). 



Though the f. linearis normally disappears in spring on the Danish shores, it 

 can however be found much later in the year if rarely. Thus I have met with it 

 on the outer side of the northern mole of Frederikshavn, near the entrance of the 

 harbour, al a place where the sea is as a rule agitated, in July 1895 and September 

 1892. The specimens found in September were very well developed, up to 30 cm. 

 long, 0,5 to 1,3 cm. broad, fully typical, only of a lighter colour than the specimens 

 occurring in winter. These discoveries, however, may be very rare exceptions, for 

 I have otherwise never found this form in summer al Frederikshavn , one of the 

 best investigated localities in Denmark, as little as in any other locality. Areschoug 

 has also found it in August on the shore of Bohuslan (Phyc. scand. mar. p. 180). 



This species has been met with hi all the monliis of the year, and it occurs 

 at all seasons in fully developed specimens. It can probably attain an age of more 

 than one year, but most of the specimens die, as said above, at a rather young 

 age. It has been found fertile at all seasons, and then nearly always with sexual 

 organs (or carpospores). While several authors slate that the species is as a rule 

 dioecious (Thi uet, Behtuolu, Kyein), I have found it most frequently monoecious 

 on the Danish shores, at all events in summer. In winter only have I found the 

 specimens generally dioecious, particularly W linearis (Plate II fig. 2 — 3). In the spe- 

 cimens met with in summer Ihe frond is generally divided by a longitudinal limiting 

 line into a male and a female portion, distinguishable thereby that the margin of the 

 lirsl is yellowish while, thai of the second purple. The limiting line is most often re- 

 markably slraighl; it is very distinct towards the margin, while downwards it be- 

 comes indistinct and finally vanishes on reaching the sterile portion of the frond 

 (Plate I tig. 1). The male and female [)arls of the frond are in some cases of equal 

 size, in others the male or the female is broadest. Even the narrow winter forms 

 can be monoecious and show a well marked limiting line (Plate II tig. 1). According 

 to Hus (1902, [). 197), the sporocarpia and anlheridia in Porphijra laciniala {umbili- 

 calis), when they are developed in the same frond, "occur in patches very much 

 as in P. perforata". If that is really normal to the species of the Pacific coast, it 

 must be supposed that it is a different species from the European P. umbilicalis. 



The decoloration of the developing antheridia generally takes place gradually 

 from the margin inwards. Some few specimens from Helsingor showed however, 

 at some distance from the margin, some lighter spots, reminding one of the an- 



