THE BRYOPHYTA OF ICELAND 559 



-svoven Nvith mosses and hepatics, and difTerent piants such as 

 Vacciniiim spp., Betula nana, Comarum palustre and several Carices 

 then establishing themselves upon these cushions. 



The numerous hepatics which occur are everywhere found 

 interspersed in the moss carpet, especially in that upon the knolis, 

 and, as regards all the species mentioned beiow, doubtless also in 

 the ground vegetation between the knolis. 



The Bryophyte Vegetation of Knolls^ is dependent upon 

 the varN'ing degiee of moisture, \vhich is greatest on the ground 

 between the knoils and least in their uppermost part. Some of the 

 Bryophyta of the ground do not ascend higher than to the base 

 of the knolis, \vhile others, especially many of the pleurocarpous 

 mosses, occur with equal frequency upon and between the knoils. 

 In addition to the latter mosses the following species are found upon 

 the knolis: — 



*Hypnum uncinatum *Mnium hornum 



— imponens *Rhacomitrium canescens 



*Climacium dendroides * — hypnoides 



*Hylocomium squarrosum *Ditrichum flexicaule 



* — parietinum *Dicranum scoparium 



* — proliferum * — congestum 

 Orthothecium chryseum (N. Icel ) * — elongatum 



*Pol3'trichum alpinum *Lopliozia lycopodioides 



* — strictum *Plagiochila asplenioides 



* — juniperinum *Ptilidium ciliare, 

 *Aulacomnium palustre 



and besides these, numerous other species which belong to other 

 formations and must rather be regarded as casual Aisitors. 



The following examples will show the composition of the bog 

 vegetation in the difTerent parts of Iceland : — 



1. Skålholt in SW. Iceland. The country here over a wide 

 expanse is covered with vast boggy areas in which small, protrud- 



^ Accordiiig to my observations these knoils are formed either by soil accu- 

 mulating in tufts of Sphagnum, etc, in which other piants take root. among 

 others sedges, when soil again accumulates, or bj* soil accumulating directh* 

 around roots of sedge-tussocks. This accumulation of soil and piants continues 

 till big knoils are formed. some 60 — 70 cm. in height. These kuolls occur in all 

 stages of development, from tufts or tussocks with a slight accumulation of soil 

 around their roots to completeh' rounded knoils in which the tussocks have en- 

 tireh' disappeared. In Danish '"Tue" stands both for "knoU"' and for 'tuft" and 

 '"tussock", which is verj' convenient when referring to one of the various stages 

 of these "knoils'. But the rendering into English has been difficult, though in each 

 case the term most appropriate to the stage of development of the "knoU" has 

 been carefullv chosen. 



