Plants, which have considerable facilities for passing over the sea, are somewhat intermediate in proportionate numbers, there being about 970 flowering plants and ferns in Ireland to 1,425 in Great Britain,--or almost exactly two-thirds, a proportion intermediate between that presented by the birds and the mammalia. _Peculiar British Birds._--Among our native mammalia, reptiles, and amphibia, it is the opinion of the best authorities that we possess neither a distinct species nor distinguishable variety. In birds, however, the case is different, since some of our species, in particular our coal-tit and long-tailed tit, present well-marked differences of colour as compared with continental specimens; and in Mr. Dresser's work on the _Birds of Europe_ they are considered to be distinct species, while Professor Newton, in his new edition of Yarrell's _British Birds_, does not consider the difference to be sufficiently great or sufficiently constant to warrant this, and therefore classes {340} them as insular races of the continental species. We have, however, one undoubted case of a bird peculiar to the British Isles, in the red grouse (_Lagopus scoticus_), which abounds in Scotland, Ireland, the north of England, and Wales, and is very distinct from any continental species, although closely allied to the willow grouse of Scandinavia. This latter species resembles it considerably in its summer plumage, but becomes pure white in winter; whereas our species retains its dark plumage throughout the year, becoming even darker in winter than in summer. We have here therefore a most interesting example of an insular form in our own country; but it is difficult to determine how it originated. On the one hand, it may be an old continental species which during the glacial epoch found a refuge here when driven from its native haunts by the advancing ice; or, on the other hand, it may be a descendant of the Northern willow grouse, which has lost its power of turning white in winter owing to its long residence in the lowlands of an island where there is little permanent snow, and where assimilation in colour to the heather among which it lurks is at all times its best protection. In either case it is equally interesting, as the one large and handsome bird which is peculiar to our islands notwithstanding their recent separation from the continent. The following is a list of the birds now held to be peculiar to the British Isles:-- 1. Parus ater, _sub. sp._ BRITANNICUS Closely allied to _P. ater_ of the continent; a local race or sub-species. 2. Acredula caudata, _sub. sp._ ROSEA Allied to _A. caudata_ of the continent. 3. LAGOPUS SCOTICUS Allied to _L. albus_ of Scandinavia, a distinct species.