462 A. HESSELBO 



91. Rhacomitrium hypnoides (L.) Lindb. 

 Grimmia hypnoides Lindb.; Rhacomitrium laniiginosiim (Ehrh.) Brid. 



Ver\' common over the whole of Iceland. 



Rhacomitiinm hyj)noi(les is by far the most common plant in Ice- 

 land. In all parts of the country, both along the coasts and on the 

 mountain heights, it covers, almost without any mixture of other piants, 

 vast tracts of land — the Grimmia heaths so well-known also from 

 other Arctic countries — with its thick greyish-white mats. It also 

 occurs in almost every locality where it is not too damp, and very 

 often intermixed in tufts of other mosses. Thus, it is very common on 

 rocks and stones, and often covers large tracts of lava-fields with 

 cushions one foot deep. In bogs it grows, as a rule, on the top of the 

 knolis, in company with species of Hylocomiiim, and in birch cop- 

 pices it forms, in association with Hylocomiiim spp, Hypniim uncinatum 

 and several other species, the moss carpet of the floor. Only sterile 

 specimens have been found. 



92. Rhacomitrium fasciculare (Schrad.) Brid. 



Very common in the Southern, Western and Eastern parts of Ice- 

 land. In X. and XW. Iceland it appears to be somewhat less plentiful, 

 but neverthelcss it must also there be regarded as one of the more 

 commonly occurring species. 



It occurs at all altitudes up to the limit of vegetation on mountain 

 heights. It forms, there, like R. sudeticnm, black Alpine forms on 

 dry rocks. 



This species usually grows on stones and rocks in dry situations, 

 but it also occurs frcqucntly in gravelly soil. Occasionally it mav 

 even be found in the lowermost portion of birch-trunks. The fruit, 

 which is rathcr common, ripens in the lowlands in the first half of June. 



93. Rhacomitrium aciculare (L.) Brid. 



Very common on wct rocks in and by rivers and waterfalls everj- 

 where in the low-lying parts of the country. It does not appear to 

 ascend uuich higher than 300—400 metres. The fruit, which occurs 

 everywhere, ripens, as a rulc, in the beginning of June. 



Xote. Grimmia (Rhacomitrium) elliptica is recorded in older lists 

 as found in Iceland by Morch. The specimens in the collections belong 

 to R. fasciculare. 



Cincliclotus fontimiloidcs , also, is recorded by Hornemann as 

 found in Iceland, but it was undoubtedly confused with another species. 

 Specimens aic not to be found in the collections. 



94. Hedwigia albicans (Web.) Lindb. 

 Hedwigia ciliata Ehrh. 

 SW. Iceland: Hafnarfjordur ,Grl.)!, sterile. 



