1898- 1902. No. 19.] STRAY CONTRIBUT. TO THE BOTANY OF N. DEVON. 15 



mentioned as sterile in all my collections are 7 acrocarp ones, which 

 perhaps fruit somewhere in the neighbourhood. At all events, the per- 

 centage of species that are found fruiting in the collections as a whole, 

 is unsually large among the mosses from the islands, which decidedly 

 speaks in favour of the supposition that only spores can be carried so 

 far by wind, not fragments of moss plants. 



There are, however, also 11 species of pleurocarpic mosses found 

 in the islands, which are entirely sterile throughout my collections and 

 which are generally found so in the Arctic Regions. If we would find 

 the means of migration which these have used for reaching the small 

 islands, I think we must look to the birds. Even if we leave out the 

 snow-bunting, which probably breeds on Castle Island, and certainly 

 pays visits to both, as well as the ptarmigans which may casually fly 

 over the strait, we have the gulls left which fly backwards and forwards 

 between their rookeries and the mainland, especially to some lakes near 

 Mount Belcher, the only locality where we found trout. Now I do not 

 think that the birds often carry seeds or other parts of plants with them 

 casually, even though it cannot be denied that they might do so, but I 

 cannot but think, that they have at some time, when the islands were 

 smaller than they are now and consisted of more isolated, bare rocks, 

 carried nestbuilding material thither from the mainland. And that 

 material, most probably, consisted of mosses, especially of the larger 

 kinds, that is to say the pleurocarpic ones, for instance the Hypna. 

 But among the moss, might easily be carried seeds and fragments of 

 such plants as are generally found growing among moss, viz. the species 

 really growing here. Thus I think the islands got their first flora, some 

 of the mosses and the flowering plants. Afterwards, when these first 

 immigrants had spreed in the island, the gulls had no further occasion 

 for procuring the material for their nests (which, moreover, are used 

 year after year) from afar, and now immigration by means of 

 the wind only could take place. But the wind carries only very small 

 bodies such as spores, and therefore the flora, which is still in the act 

 of receiving new species of fruiting mosses, has become comparatively 

 richer in such species than in other plants; and the percentage of mosses 

 in the flora as a whole, is larger here than in that of the adjacent points 

 in the mainland which in other respects offer the same conditions of life. 



Of course the immigration of these plants which have used the wind 

 as a means of conveyance, fruiting mosses, freshwater algae, and lichens, 

 also dates from far back, the last-mentioned having probably been the 

 very first colonists. One mode of conveyance I have entirely left out 



