278 joiis. M()¥i; i'i;ii;usi;.\ 



11)09 p. 11) and iii Arj<entiiH> l'.or'^i- l'.MKl. p. '.!) IU«si(ics il has oricii 

 bcen found in hrackish waler and also in Irisii waUiv 



Wlu'lhcr /'. Ilenniiinsii Lcinni. l'.Mt) p 124 artually can l)C di- 

 slin;*nislHMl from P. fhiiiilc doni is lii^^l'ly (|ncsti()nal)ie. Tlie sole dis- 

 linjinishin.U charaitcr. wliicli I can lind in Ihc dcscriplion. is the appea- 

 rance of llic shcallis whirli in llu- former are considercd to be lirm. in 

 the latter diflUient. Hnl siich a cliaracler can liardly he nlili/.ed here 

 as a basis of dislinction as numcrons species now have lirm, now dif- 

 lUient shealhs. 



Phormidium luridum Kiitz (lom. 



(ioniont, .Munu^r. II p. 10.'), pi. IV, li^s. 17, IS. 



\V. Iccl. Hveravcllir, lemp. 38 " C. West 1902 p. 244). 

 Area: Kur., As., Am., Austr. 



This species, which is only nicntioned from aboul half a do/.en lo- 

 calities, I have not been able to lind in Iceland. The main disUnctive 

 character, by means of which it can be dislini^nished from the olher 

 Ihin species of PJwrmidiiim, is evidently the ^'olour of Ihe Ihalhis. The 

 localities, on which it occurs, are ralher varied, so that it is dill'icult 

 to foini any opinion on tiie basis of the statements in Ihe literature as 

 to which conditions are most favourai)le for ils growlh. l'erhaps it will 

 ajipcar that this species has a wider liislribution in hot sprinj>s as we 

 now know. Laler it has been found in a hot spring on the Feejee Is- 

 lands, lemp. 59° C. (West in Gibbs 1909 p. 202.) 



* 



Phormidium laminosum Ag^ Gom. 



Gomonl, Monogr. II p. 167, pi. IV, hgs. 21, 22. Ostenfeld 1899 p. 238. 



N. Icel. Outlel from Uxahver. temp. 35 ^ and 42*^ ^^/i 1914.— W. 

 Icel. Oullet from "Skrilla" at Reykholt, temp. 25'' -'s 1914. Hveravcllir, 

 temp. 24** C. (West 1902 p. 245).— S. Icel. Reykjavik, Laugarnar, 40'^ C. 

 ^'/lo 1897 (H. J.)! Ibid., ^6 1896 C. H. O. ! 



Area: All continents, Antarctic, Si)it/.bergen. Alaska. 



To dislinguisii I*. Idminosiim from P. Iciuic is oflen allendcd wilh 

 consideiahk' dillicullies partly bccause Ihey are bolh possessed of extre- 

 mely thin Irichomes. parlly because llu- distinguishing characters cnnnot 

 ahvays be seen wilh sulficient distinclness. Therefore it has bcen ne- 

 cessary to leave a nuniber of sjiccimens undcleiniincd. allhough great 

 pains have bcen beslowcd on the tlctcrminalion. 



From Iceland Ihc species is only known from Ihe hol springs, and 

 on that kind of localily il has a world-wide »lislribulion, and Hlenkin 

 (1914 menlions il togelher wilh lldpalnsiphon htmiiiostis as cosmojjolile 

 among Ihc tlu'rm(>|)hilous algae. l-urtluM more il is also supi)()sed to 

 occur in cold fresh water, on moist rocks or between mosscs. Finally 

 Miss Bristol 1920 p. 59) has found it in a sample from cultivated soil 

 in Knghind. 



In Iceland I have found it al Icmpci alurcs lying Ijclween 25 " and 

 42 ''. On the basis of lileralure il is dillicult to draw any conclusions, 

 as to the niaximum of temi)erature at which it is abic lo thrive, owing 

 to the fad thai oftcn but Ihc temperature of Ihe spring is stated without 



