'.HV2 JOMS. HOlfK l'KTERSEN 



(Hl llu' lloor of tlu> riivo. The iilj^nl vegetation liere eoiisisled ol' 

 liumillcrid rxilis. Hmnillcriopsis hrcius. Hormidiuui /hnridmn, and 

 several Diatonis, sonie ol llie iisiial nitrojiliiious sjiecics sucli as 

 Sauicuhi Alonuis and forms ol" A'. iniilicd. and a few ol' tliose usually 

 f^roNvin«? on rocks siuli as Fracjilaria hrnissinui. Mclosird lioescaiia, 

 Xaificula conlento. In tlie ollicr eave (184, Ski'ilnstai'Mr) lliere were 

 no distinel traces ol" slieep, but it is probable Ibat they used this 

 cave as a slielter, too. In tlie loose soil here lliere occnired nioss- 

 protonenia and sonie Diatonis, aniong \vliicli forms ol Xariciihi 

 miiticd and PiniuiUiria intennedia \vere tlie comnionesl. 



Essentially dilVerent \vas Ihe vegetation in a small (basalt?) cave 

 near tlie farm Mj()anes (E. Iceland). Here llie waler dripped con- 

 linually from the roof of llie cave and tricklcd down llie walls. 

 Hence llie algal vegetation here bore a slrongly liydropliilous cha- 

 racter. Of green algæ I found Honnidhim fldccidnm, Ulolhrix zoiuitd, 

 and Trihonenid boinbijcinniu besides nunierous Diatonis, aniong 

 Nvhicli Meridian circularc was the comnionest. 



By the shore norlh-easl of Hiisavik I found a cave in palagonile- 

 breccia, evidenlly fornied by the action of the waves (243). Al the 

 lime ol niy visit il was (piile dry, bolh Ihe floor and the \valls 

 of it. Here I found Siichococcus bdcilldiis wliich usually thrives well 

 in a (lim light, and Xaviciihi miilicd f. mininid in a peculiar form 

 willi poinled apices. 



Al Heimaey (Vestmannaeyjar) I had the opporlunity of examining 

 a couple of rocky caves (399, 401, 403) in the ^veslern wall of Heinia- 

 klellur al a lieighl of about 20 m. They were old caves waslied 

 out by Ihe waves bul could nol iiow be reached by the salt water 

 on account of the elevation of the land lliat has laken place in 

 recent limes. (Helgi .huisson 1911, p. 122). Il is possible, however, 

 thai very fine salt waler spray may reach Ihem in slormy wealher. 

 The vegetation had parlly a halophilous character. On llie floor of 

 oiie cave was a green carpet consisling of lihizocloninm Idpponicum 

 and Vducherid sijnandrd aniong wliich lliere were numerous Dia- 

 loms. \Ve shall mcnlion Acltiidnthes delicaluht, C.dloncis fascidid, 

 S'auicnln peregrind n. Mcniscus. On the hard rocky wall of the same 

 cave Ihere was likewise an abundant vegetation of Diatoms con- 

 sisling parlly of the usual pelrophilous species sucli as Achndnlhes 

 codrcfdid , Hdntzschid dn^phinxija, Xanicnla cincld i>. Hen/leri. X. con- 

 lentd, Xdvicnid perpnsilld, Pinnnhirid iniennedid, and P. pdrvd v. Laijer- 

 sledlii /. inlcrrnpld, partly halophilous species such as Nauiciila cinda, 



