MARINE ALGAL VEGETATION 1 73 



Group 3. Species which carry on vegetative and reproductive 

 work only during a part of the year. 



In referring the Icelandic species to these groups the difficulty 

 at once arises, that we lack knowledge regarding the behaviour of 

 a number of the species during winter. Such species cannot there- 

 fore be grouped with any certainty at the present time. True, we 

 may judge with some probability how they behave here during 

 winter by a comparison of their winter-activities in other places, 

 provided these are known ; but as it has been shown that one and 

 the same species often behaves differently in two distantly situated 

 places, a satisfactory result could not be arrived at through such 

 a comparison which has, for that reason, been omitted. I therefore 

 mention a few species only, which I think I can group with some 

 certainty. 



Group 1. The following species belong to this group: — Hilden- 

 brandia rosea which fruits all the year round. Rhodymenia palmata; 

 it might appear doubtful whether this species should be classed as 

 a perennial. Kjellman (36, p. 150) regards it as an annual plant 

 which forms tetraspores twice, once as a young plant and the 

 second time just before it dies. It appears to me that the new 

 shoots which arise early in spring from evidently old fronds, show 

 that it lives through at any rate more than one period of growth. 

 Pelvetia canaliculata bears fruit and carries on vegetative work the 

 whole year at Reykjavik. In December — January the fruiting indi- 

 viduals were comparatively few, but there was a quantity of young 

 plants almost all of which were in the "rosette" stage. It is per- 

 haps doubtful if this species belongs to this group at all. 



Group 2. The Fucacece belong to this group (with the exception 

 of Pelvetia (?)). Fucus spiralis produces fruit in spring, summer and 

 autumn. In December (1911) it was sterile, and young plants were 

 found in quantities. 



Ascophyllum nodosum, Fucus vesiculosus and Fucus inflatus, all 

 these behave almost similarly. In December and January I saw, 

 here and there, individuals with very young receptacles, but by far 

 the greater part were sterile. In spring and early summer these 

 species are found everywhere with full-grown receptacles. In the 

 latter half of August they are sterile everywhere and at that time 

 only a few individuals, which must be regarded as stragglers, are 

 found bearing receptacles. Of F. inflatus I saw no stragglers in Au- 

 gust. In September also they are sterile. In the first half of October 



