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 | 
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 
