420 



.ions. BOiK PKTKRSEN 



('.onjujiatav 



In a niimbcr ol' llic saiu|)les. cspeci:ill\ tliosc liom liilts ut iiioss 

 round hot springs, llierc occurrcd somo Desmidiciccæ. Mr. .1 \ v j^a n rd 

 havinj,' hocn char^'cd willi ihe elaljoration of this group of algæ, 1 have 

 nol includod llicm in [Uc syslcnialir siirvev of Ihe species, but in tlie 

 list of thc species I luenlion under the samples in (|uesti()ii wiien Des- 

 midiaceæ occiir in liieni. Mr. Nygaard will then niake Ihe determina- 

 tions and incorjjorate these species in tlie colleelive list ot" llie Icelandic 

 D(Siui(li(ircir. 



Zygogonium ericetorum Kiitz. O. Horge und l'aseher 1913, p. 37. 

 H. Icel. 129 - W. Icel, 302. 



The species is evidently nol conimon in heland. I found some few 

 threads on a rocky wall in Vesldalur 029), and a larger (pianlitv in a 

 dried uj) pu(hlle near Geitaberg. (302). 



Heterocontæ. 



Botrydiopsis arhiza Fiorzi. Borzi 1S95, p. 170, Tav. 12. 13. Pascher 

 Susswasserllora Helt. 11. p. 44. 



X. Icel. 2a6 - W. kel. 33(3. 338 - S. Icel. 287. 



Forms yellowish-red jxtwdery layers on rocks, earlh. and woodwork. 

 The layer consists of spherical cells having a diameter of 4-34 ti. In all 

 the sam|)les mentioned above the cells were lilled wilh drops of oil and 

 other nulrient substances. and were thus in the resting stage, i Borzi, 

 1. c. Tav. 13. lig. 12. 19). In some few cells thc numerous chromatophores 

 could be distinguished after the addition of chlor-zinc-iodine. In a few 

 cells the cell contents had divided into a number of small cells (zoo- 

 spores? . Horzi found the species on irrorated rocks. 



Evidently the species only vegetates and multiplies in damp periods, 

 but when it has been dry for some lime, the cells may arm themselves 

 against de<iiccalion by passing into the resting stage. 



Botrydium granulatum L.i Grev. Klebs 1890 p. 223. Fa.scher, Suss- 

 wasserllora Heil. 11. 192;"). p. 117. lig. 9(5. 1-4. 



S. Icel. 387. 



This species having previously been conlused wilh Pmlosiphon, 

 Klebs 189(5. p. 169, it is diflicult lo gather any information from the 

 hterature as to its geographical distribution. It can hardly be doubtcd 

 that it has a very wide distribution, yet it would seem Ihat so far it 

 has only been known from temperate and warmer climatcs. whereas it 

 has not i)reviously been Hmnd in any place having an arctic or subarc- 

 tic climale. 



B. f/mnuldlnm is habitually found on damp, clayey ground, and thc 

 above-menlioned sample originales from a similar locality. 



