THE FIIKSH-WATER CYANOPHYCEÆ OF ICKLANU 



281 



conditions and presumably other species of Phorniidiiim mav also occur 

 in a manner corresponding to that of P. Treleasei at Klepjijarnsreykir. 

 Tilden (1897 p. 194) describes siniilar formations in P. laminosiim. Never- 

 theless, I do not consider it to be quite excluded that it, in reality, 

 was P. Treleasei that was present. Judging by Tildens figure (pi. VIII, 

 fig. 8) the cells were 

 much too long for P. la- 

 minosiim, but of suitable 

 length for P. Treleasei. 

 To keep these two spe- 

 cies apart is, for the rest, 

 extremcly difficult. P. 

 Treleasei is only known 

 from hot springs. 



Phormidium ramo- 

 sum Boye P. n. sp. 



Ph. thallis ramosis 

 penicillatis, fluctuanti- 

 bus, laete æruginosis, tilis 

 0.1—1 mm. crassis; va- 

 ginis plerumque in mn- 

 cum amorphum diflluen- 

 tibus, chlorozincico jo- 

 duralo non coerulescen- 

 tibus; trichomatibus api- 

 cibus rectis, parallelis 

 vel varie intricatis, rectis 

 vel curvatis, 1.3—1.9 fi 

 crassis, cylindricis, ad 

 genicula non constrictis, 

 dissepimentis sæpe in- 

 conspicuis, articulis dia- 

 metro trichomatis 2—3- 

 plo longioribus, proto- 

 plasmate homogeneo vel 

 granulis pancis instructo; 

 cellula apicali rotundata, 

 membranam superne in- 

 crassatam præbente. 



S. Icel. Laugarvatn, 



Fig. 3. Phormidium ramosiim n. sp. 

 Tlialhis (natural size). 



in outlet from a Laug, temp. 36 *^ ^''/s 1914. 

 Reykjavik, Laugarne, temp. 35° ^/s 1914? 



The colour of the dried thallus almost corresponded to Codex nr. 

 328. In the sample from Reykjavik a large number of Oscillaloria pro- 

 boscidea var. Westii occur besides the species in question, and this is 

 perhaps the reason why it has not on this locality assumed the 

 branched floccose form. In the sample from Laugarvatn its habit reminds 

 extremely of P. Rclzii Gom. f. fascicnlata Gom. 1893 p. LXXXVI, pi. IV, 

 fig. 1—2); but the trichomes are far 



The Botanv of Iccland. Vol. 11. 



thinner than in this species, so 



19 



