492 A. HESSELBO 



on wet sandy or gravellj' ground and on damp rocks. In the greater 

 part of Ihe country it is very comnion in siich localities; only in NW. 

 Iceland and partly in S. Iceland does it occur more scantily. for instance 

 on Fljotshlid and below Eyjafjall. It is most Irequent in the low land, 

 but nevertheless often ascends up to a height of 500 — 600 metres above 

 sea-level. The fruit. which is always present plentifulh^, ripcns at the 

 end of July. 



181. Meesea triquetra (L.) Ångstr. 

 Meesea tris tic ha Br. eur. 



Common in E. and N. Iceland!. NW. Iceland, Arngerdareyri!; W. 

 Iceland: frequcnt about Reykjavik and Esja!; rarer and most scanty in 

 S. Iceland. 



It grows on boggy ground, sometimes in small unmixed tufts, some- 

 times intermixed with other mosses such as Hypnacece, Paliidella, Mniiim 

 af fine, etc. Only sterile specimens have been found. 



182. Catoscopium nigritum (Hedw.) Brid. 



Ver}' common in E., X. and W. Iceland, more rare and rather scanty 

 in NW. and S. Iceland. It grows on wet boggy ground, where it some- 

 times forms very dense tufts about 8—10 cm. high, sometimes grows 

 interspersed in tufts of other mosses. It occasionally occurs so abun- 

 dantly, especially in N. Iceland, that it may form the main part of the 

 vegetation in the bogs. 



Gronlund records that this species is one of the character-plants 

 of the warm ground, and C.Jensen (Bot. Tid. XIV 1885) has described 

 a var. Gronlundii: 'Tiliformis, humilis, superne flavescens, inferne nigre- 

 scens. Folia subremota imbricata, minima, ovata lanceolata, integra vel 

 subintegra, costa crassa in apicem evanida, cellulis minoz'ibus, incras- 

 satis et papillosis," which was collecled by Gronlund near a hot spring 

 in Reykholtdalur. In Gronlund's collections in the Botanical Museum 

 in Copenhagen there are some mosses determined as Catoscopium nigri- 

 tum or C. nigritum var. Gronlundii from a warm substratum. Of these 

 only one specimen from Reykholtdalur belongs to var. Gronlundii, and 

 I have collected similar forms rather scantily near other hot springs. 

 This form differs only slightly from the type, chiefly only in being less 

 tomentose and in having shorter leaves. Almost all the other specimens 

 of Catosco])ium collected by Gronlund were wrongly determined, as 

 they belong to Archidium phascoides , and on the whole Catoscopium 

 occurs only accidentally and scantily on a warm substratum. 



The fruit, which occurs very frequently and plentifully, was in 

 June-July either old and emptied from the prcvious year or yet quite 

 unripe. 



183. Conostomum boreale Swartz. 



Conostomum tetragonum (Vill.) Lindb. 



Widely distributed over the whole of Iceland 



In W. and S. Iceland this species is found only by exception at a 



