THE FRESH-WATER CYANOPHYCEÆ OF ICELAND 



291 



The species has only been found a few times, viz. originallj- by 

 Heufler near Kufstein in the Tyrol, and Griinow described it from this 

 specimen. This is the only one which Gomont knows. Almost simul- 

 taneously with the appearance of Gomont's Monographie, Hansgirg (Pro- 

 dromus II p. 92) published a Lijngbija nigrovaginata which later was 

 established by A. Forti (in De-Toni Syll. Alg. V p. 365) as being synony- 

 mous with S. Heufleri. Hansgirg has found the species in several piaces 

 in Bohemia. It grew everywhere on more or less moist rocks. 



On the Icelandic locality it grew together with Gloeocapsa alpina, 

 Scytonema crustaceiim, Calothrix parietina and Nostoc sp. and formed to- 

 gether with those thin black crusts which were scraped of the rock 

 only with difficulty. ' 



Schizothrix sp. 



In a sample from S6marstat)ir i^E. Icel.) ^^/e 1894 (H. J.)! I found 

 among Zygnema, Tribonema and other algæ a Schizothrix with quite 

 thin trichomes (ca. 1 // in diameter) the cells of which were somewhat 

 longer than the diameter. As a rule only one trichome occurred in 

 each sheath, at times, however, 2—3. Chlor-zinc-iodine coloured the 

 sheaths violet, though not a particularly deep violet, and they were 

 often distinctly closed at the apex. 



There is a probability that it may be the finest branches of a Schi- 

 zothrix lacnstris A. Braun, but I don't, however, feel justified in identi- 

 fying the alga from S6marsta5ir with this species as it is so incomple- 

 tely developed. Besides, there exists so many incompletely described 

 Schizothrix species, the identity of which only will be ascertained with 

 great difficulty, if ever, that I do not feel inclined to increase their 

 number by also describing the present form as a new species. 



VII. Hydrocoleum Kiitzing. 



Gomont, Mo- 





Hydrocoleum homoeotrichum Kutz. 

 Kiitzing Tab. phyc. I, tab. 50, fig. 1. 

 nogr. I p. 344. 



E. Icel. Vallanes, on stones from the margin of La- 

 garfljot "/e 1893 and ^Vs 1894 (H. J.)! 

 Area: Eur., Afr., N. Am., Austr. 



The present form seems to differ slightly from the 

 typical Hydrocoleum homoeotrichum by its rounded calyp- 

 tra. Also the dimensions of the trichomes are slightly de- 

 viating in that their diameter is 4—7 /li. (Fig. 8.) 



It occurs as a rule in cold, rapid mountain torrents, 

 often together with Hydrurus foetidus. The Icelandic oc- Hydrocoleum 

 currence is in good accordance with the above statement, homoeotrichum 

 as Lagarfljot Carries the milky water from the inland gla- 

 ciers and thercfore always has a low temp. (8*^ ^^/e 1914). 



Fig. 8. 



Kiitz formå 

 (X1'200) 



