THE FRESH-WATER CYANOPHYCEÆ OF ICELAxND 263 



or whether the brown sheaths must first split and peel ofT bei'orc a 

 reprodiiction can take place. 



II. Chroococcus Nag. 



Chroococcus turgidus (Kiitz.) Nag. 



Lemniermann 1910 p. 53. Kutz. Tab. Phyc. I, tab. 6. Wittr. et Nordst. 

 Alg. exsicc. no. 100, 250, 472, 699, 799. Phycotheca polonica no. l'. 



Chroococcus tnrgidiis var. chalybeus Hauck et Richter Phycotheca uni- 

 vers, no. 145. 



Chroococcus chalybeus Rab. Alg. Eur. no. 1144. 



E. Icel. Rocky wall over which water was trickling Fljotsdalur ^Vs 

 1914.— N. Icel. Pond near Grimstaåir at Myvatn -^/t 1914. Brennisteins- 

 tjorn near Geitej'jarstrond (Myvatn) temp. 18*^. In plankton. — N. W. Icel. 

 Arnarfjorc)ur Belloc U894), Hariot (1893 p. 314). 



Area: Ubiquist, Færoes, Novaya Zemlya, Lappland, Spitzbergen, 

 Greenland, Alaska. 



According to literature this species is one of the most pronounced 

 ubiquists of the blue-green algae also in respect to its being able to 

 grow under highly varying conditions. Thus it occurs in bogs as well 

 as in lakes, in benthos as well as in plankton and as semi-aérophilous 

 alga on damp rock-walls. Bohlin (1901 p. 10) characterizes it as a 

 "sphagnophilous", and Reiter (1919 p. 183, 190) as well as Steinecke (1916 

 p. 24) incline towards the same opinion, whereas others, for instance, 

 KufTerath (1914 p. 262) considers it to be actually calciphilous (cf. 

 Steiner 1911 p. 5). The conllicting views are perhaps due to the faet 

 that we have not to do with a single species, but with several re- 

 sembling each other closely. 



On examining a series of exsiccata and determining the colour of 

 the cell contents, the stratilication of the sheath and its reaction 

 to chlor-zinc-iodine, I have been able to distinguish a special form 

 which I suppose to be identical with Chroococcus turgidus var. uiolaceus 

 W. West (1892). I describe this form as a new species under the name 

 C. Westii. Microscopic examinations showed the genuine C. turgidus ex- 

 siccata to be of a colour which mainly corresponds to Codex no. 356; 

 in a few cases, however, the colour was obviously bleached in the 

 course of time. In one case only it was possible to get a somewhat 

 reliable macroscopic determination of the colour, viz. Hauck et Richter 

 Phycotheca univers, no. 145, in which a sufficiently "pure" sample was 

 found i. e. not containing other algae or impurity. The colour of the 

 plant-mass almost corresponded to Codex no. 326. In all the cases the 

 sheath proved to be absolutely hyaline and indistinctly or not at all 

 stratified. When treated with chlor-zinc-iodine it swelled more or less 

 or dissolved entirel3% at times it assumed a very faint bluish tone. 



According to Virieux (1910 p. 335) the sheath should consist of 

 pectin substances. My investigations seem to prove that it at times 

 may contain faint indications of a cellulose-like substance. 



Chroococcus Westii Boye P. n. sp. 



Chroococcus turgidus var. uiolaceus W. West (1892 p. 741)?. 

 — _ . _ Schorler (1914 p. 16)?. 



