114 CARL SKOTTSBERG, A BOTANICAL SURVEY OF THE FALKLAND ISLANDS. 



siderably smaller than is generally the case and most of them showed traces of the 

 rigours of the climate. 



As an appendix I shall give a description of the vegetation on stony slopes, 

 vvhere after periods of rain the ground becomes partly converted into flovving soil. 

 This is a typical »Polsterboden», the principal members form ing härd cushions. 

 Between them the soil, wliich is a mixture of small stones, gravel, sand and clay, 

 lies bare, with only solitary grasses or herbs appearing. 



12. Slope near the sea on New Island. The ball-shaped cushions were often 

 formed by several species growing together. 



Cop. Bolax gummifera Festuca magellanica Asorella fdamentosa f. maritima 



Nassauvia Gauäichaudii Sol. Accena magellanica Pernettya pumila 



Spårs. AzorcUa ccespitosa Aira parrula Pratia repens (very local). 



Colobantlms suhiilatits 



The same kind of vegetation was seen on corresponding localities on West- 

 point and Beaver Islands. In the latter place there are patches of a more typical 

 flowing-soil, more mobile than that mentioned above. They bear only one species, 

 Festuca arenaria, the common grass on drift sand, where the conditions are, to some 

 extent, similar. 



The vegetation of tlie stoiie-ruiis. (Pl. IX, X: l.) 



There are, in the stone-runs, small areas with Empetrum or Cortaderia. They 

 are generally poor in species but otherwise do not differ materially from other parts 

 of meadow or heath, and I do not include them here. They are of interest as 

 serving to explain the influence of the mechanical composition of the soil, but this 

 side of the matter has already been treated by me in 1909. With the stone-runs I 

 here mean the barren block-fields. Deep down in their bottom soil has accumulated, 

 and some few species are able to germinate in the subdued light and to push their 

 long, flexible stems up among the blocks till they reach the surface of the stone-run. 

 The most noticeable of them is Nassauvia serpens with stems up to 1,5 m. long, 

 clothed with reflex, imbricate, pungent leaves all along and with few, erect branches, 

 and large, cylindrical, composed flower-heads, a most unexpected product of a barren 

 block-desert. Like this, too, grows Enargea 7narginata, and also Rubus geoides, but 

 hardiy from any greater depth. Two ferns are found in solitary tufts between the 

 blocks, Blechnum ynagellanicum and Polystichum inohrioides, both finely developed on 

 account of the good shelter. Besides, there are small mats here and there between 

 the blocks ; their vegetation is identical with the Blechnum magellanicum-aiSsocia,t\on. 

 Crevices are filled by Serpyllopsis ccespitosa, pure or mixed with petrophilous 

 mosses and lichens. The exposed sides of the blocks are covered with crustaceous 

 lichens. 



13. Stone-run on Hornby Mountains, W. F. 



Sol. -spårs. Blechnum inagellanicum, Enargea marginata, Nassauvia serpens, Poa 

 antarctia, Polystichum mohrioides, Rubus geoides, Seiiecio litoralis. 



