410 A. HESSELBO 



Haplozia creiuilata is in Iceland a decidedly warm-soil species whicla 

 is hardl\- absent from any hot spring, wliether sulphurous or alkaline. 

 It grows there in abundance on warm clayey flåts which have a tem- 

 perature of 20°— 35°, near Myvatn even at a temperature of about 40°. 

 It occurs far more rareh' on peat}' soil, and then onh' scantih\ Curi- 

 ousl}' enough, these habitats, also, are situated in districts where there 

 are liot springs. Near Laugarland, for instance at the edge of the 

 marsh, there is a small spring wUh lukewarm water, but the heat from 

 it can exert no influence on Haplozia cremilata, nor does the latter 

 occur in the immediate neighbourhood of the spring. 



This species varies considerably in colour, size, thickness of the 

 cell-walls and as regards the leaf-margin. In the low, reddish-brown 

 forms which grow on warm ground nearest to the hot water the cell- 

 walls are more highh' thickened , and are especially distinctly collen- 

 chymatous, while the more vigorous, green forms which grow at some 

 distance from the spring on more boggy ground, among other Brj'o- 

 phyta, have thin-walled cells which are indistinctly collenchymatous. 

 The marginal cells are sometimes large and thick-walled , sometimes 

 scarcely larger than the other leaf-cells and then onW slightly thickened; 

 in such cases it may be difficult to distinguish the plant from the forms 

 of Haplozia sphærocarpa and Alicularia scalaris with which it is often 

 found associated. Under high magnifjing powers the marginal cells 

 will however always be seen to be somewhat papillose, which is never 

 the case in Alicularia. 



28. Haplozia sphærocarpa (Hook.) Dum. 



S. Iceland: Grafarbakki near a hot spring (F.)!; Thorlåkshver among 

 Catharinea undiilalal: Sj'dri Reykjahver among Oligotrichiim hercynicuml; 

 Laugarvatnshver among Sphagnum cymbifoliuml; Isafjordur on a rocky 

 flat (300—400 metres above sealevel)!. 



All the forms found, which are quite sterile, stand slender and 

 erect among other Bryophyta and must doubtless be referred more 

 particularly to the type. 



This species, like its companion Oligotrichum , has a very peculiar 

 distribution in Iceland, having two such widely different areas of distri- 

 bution as the warm clayey flat with a temperature of 25°— 30° and 

 the rocky flat. 



Note. A liverwort is flgured in Flora Danica, tab. 2195, under the 

 name Jungermannia pumila; it is recorded to have been found by 

 Morch near Lejrå. Lindberg, in his critical revision of the mosses 

 in Flora Danica, refers it to Jungermannia cæspiticia, but the specimens 

 are not to be found in the collections. 



29. Haplozia cordifolia (Hook.) Dum. 



Verj' common and often fruiting richly. It grows especially on 

 rocks, in or bj'^ waterfalls; or submerged in rivers, where it sometimes 

 covers large surfaces of the firm rockj^ bottom with its blackish-green 

 mats. But it may also be met with on irrigated gravelh' ground or in 



