172 H. JONSSON 



The Fruiting Period. In the table given below is indicated 

 the time at which the species have been found in fruit. A + sig- 

 nifies that the greater part of the individuals in the samples gathered 

 were fruiting; a -*- signifies that fruiting and sterile individuals 

 occurred in almost equal abundance, or sometimes that only a few 

 fruiting individuals occurred ; a signifies that only sterile indi- 

 viduals of the species were found. 



In the majority of the annual species the fruiting period 

 coincides with the vegetative stage, and thus growing vegetative 

 shoots and sporangia are frequently found on the same individual. 

 These species fruit comparatively quickly and the young, or purely 

 vegetative, stage is of short duration. The fruiting period extends 

 over spring and summer probably in the case of the majority of 

 the species. They do not, however, behave similarly in this respect 

 in the different coastal districts. Urospora Wormskioldii, Monostroma 

 Grevillei, M. imdiilatum, Ectocarpus tomentosoides and Litosiphon fili- 

 formis are all decidedly spring plants at Reykjavik, but in E. Ice- 

 land they have been found bearing fruit far into the summer. 

 Leathesia difformis is a decidedly summer species at Reykjavik, it 

 has been observed fruiting in June, July, August and even into 

 September, but it was dying away in the middle of September. At 

 Reykjavik its life-period coincides with its fruiting-period, but in N. 

 Iceland it has- been gathered in a sterile condition in September. 

 This species appears to behave in the same manner on the west 

 coast of Sweden (Kylin, 45) as at Reykjavik. Moreover the fact 

 may be emphasized that at the latter place Enteromorpha Linza is 

 usually a summer and autumn species. 



With regard to the perennial species, it happens both that the 

 vegetative growth and the fruit-formation is simultaneous, and also 

 that the two stages occur at different times. A purely vegetative, 

 young stage, more prolonged than in the annuals, is found in 

 several of the perennials; thus, I think that I have seen indications 

 of Alaria and Laminaria species being in a purely vegetative stage 

 throughout the first year and perhaps longer. 



Kylin (45, p. 274) divides the perennial species into three groups 

 according to their life-activity: 



Group 1 includes species which carry on vegetative and repro- 

 ductive work all the year round. 



Group 2. Species which carry on vegetative work the whole 

 year, but reproductive work only for a part of the year. 



