THE FRESH-WATER CYANOPHYCEÆ OF ICELAND 259 



of microscopic examination of individual cells using an Abbes 

 camera lucida when comparing. I have exclusively used transniilted 

 light but it certainly would have been better at the same time to 

 have determined the colour in reflected Hght, that, for instance, 

 might be produced by a paraboloid condensor. 



Se hm id (1917) intioduces a new distinguishing character for 

 the various species, viz. whether their Iricliomes in movement turn 

 to the left or to the right. According to Schmid this is supposed 

 to be absolutely constant in each species. But it can only be used 

 when living material is to band, hence in the determination of 

 collections originating from expeditions and the like it is absolutely 

 inapplicable. Therefore its practical importance appears to me to 

 be rather limited. 



REMARKS ON THE INDIVIDUAL SPECIES MENTIONED BELOW. 



In the following systematic list regarding species of Cyano- 

 phijceæ found in Iceland are included: — 1) all species personally 

 observed in samples from Iceland; 2) the species that in the more 

 recent literature are mentioned as belonging to the island. 



The description as well as the illustrations and exsiccata which 

 may have been used to the determinations are cited under each 

 species. Thereupon follows a statement of the localities in Iceland 

 from where I know the species. I use the following abbreviations: 

 E. Icel. (East Iceland); N. Icel. (North Iceland); N.W. Icel. (North 

 West Iceland); W. Icel. (West Iceland); S. Icel. (South Iceland). These 

 abbreviations do not correspond to those used by Helgi Jonsson 

 (1912, p. 5) in respect to marine algae; therefore I shall quite briefl}^ 

 mention what is meant bj^ the expressions which I have mainly 

 added because the same place-names often occur in dilferent parts 

 of the island and not because a special phyto-geographical difference 

 between these districts can be expected with regard to the fresh- 

 water algae. 



When referring to East Iceland, I mean the country from Horna- 

 fjor9ur to Langanes; North Iceland extends from this point to Huna- 

 floi; N.W. Iceland is the great North-West peninsula; West Iceland 

 the country from the interior of Brei(Mfj6r5ur to almost the interior 

 of Hvalfjoråur; South Iceland the whole of the rest. In faet, it is 

 chiefly but the populated districts along the coast and the great 

 Valleys stretching inland that are as yet investigated. In the whole 



