whilst the dysgeogenous hills are more grassy and in the two upper zones it is far more usually amongst the scars of the limestone and the short grassy turf which the limestones immediately underlie that the ascending stations of the common pascual, pratal, mural and glareal plants of the low country are to be found. A glance at the botanical list will show how very frequently the Main Limestone' and the Hambleton plateau' are mentioned in connection with the ascending limits of species. And on the other hand, the heatherlands of the Central Valley are all based upon sandstone, and with them Drosera anglica, Vaccinium Oxycoccus, Listera cordata, Lycopodium Selago, L. selaginoides and several of the Montane mosses descend to their lowest stations, where they meet and mingle with such species. as Gentiana Pneumonanthe, Mentha Pulegium, Centunculus minimus, Spergularia rubra, Cerastium semidecandrum, Hypericum elodes, Radiola Millegrana, Ornithopus perpusillus, and Lycopodium inundatum. It is in the tract of the Middle Oolite that the characteristically Xerophilous species have their head-quarters. The following species are the most typical representatives of this category and are either absolutely or very nearly restricted in North Yorkshire to the scars and dry banks of the Middle Oolite, the Magnesian Limestone, and the Mountain Limestone, avoiding altogether or growing but very sparingly in the eugeogenous three-fourths of the area of the Riding. Of these forty-three species, fifteen are restricted to the West of the Central Valley and four to the East, but the remaining twenty-four grow both upon the east and the west of it. Of the distribution of the latter that of Aquilegia vulgaris will afford a fair average illustration. So far as known to me the Wild Columbine grows in North Yorkshire as follows, excluding from consideration two or three stations where it is plainly a garden escape. Amongst the western hills in Swaledale in woods at the Round Howe and on the north side of the river near Applegarth, and in the Yore district in Fossdale Woods and Shaw Gill, Hardraw, in all these cases amongst the scars of the Yoredale Limestone; and also in Wensleydale by the Yore side about the Aysgarth rapids upon the Lower Scar Limestone. From the tract underlaid by the Millstone Grit series it is altogether absent. Where the Magnesian Limestone comes to the surface it grows in woods by the Wharfe side at Thorparch. It overleaps altogether the New Red Sandstone of the Central Valley and is absent also from the tracts underlaid by the Lias and the Inferior Oolite. Amongst the woods of the calcareous embankments of the hills of the Middle Oolite it grows plentifully in Yowlasdale, Beckdale and several other places about Helmsley and Hawnby and Pickering, in the Howardian tract in several stations, and in the dale of the Derwent near Hackness. From the Vale of Pickering it is altogether absent. So that we have the plant growing more or less abundantly in all the tracts (see table at page 51) which are underlaid by the dysgeogenous beds, but entirely absent from the wide intermediate areas underlaid by the more porous and more humid strata. It follows the limestone from east to west through the irregularities of its dispersion and is entirely restricted to that fourth portion of the area of North Yorkshire to which the limestone is restricted. How closely the distribution of many of these Xerophilous species corresponds with that of Aquilegia a glance at what is said respecting them in the botanical portion of these notes will shew. The following species shew clearly a similar lithological restriction, but not in a manner so decidedly marked as in the case of those which have already been named. In these two lists aboriginally native species only have been included and together they take in about one in thirteen of our indigenous flowering plants and ferns. When these species pass beyond the limits of the dysgeogenous fourth of North Yorkshire they always grow over dry sandy rock or dry sandy or gravelly detritus, avoiding the clayey and rich heavy soils. Next to the immediate neighbourhood of compact calcareous rock they evidently prefer stations where sand so loosely bound : together that water sinks readily through it predominates, a circumstance which indicates pretty conclusively that it is the dryness of the limestones rather than their chemical composition which is the chief source of attraction. Several of them are to be met with upon the coast sand-hills in the neighbourhood of Redcar: a few of them are found in the vicinity of the basaltic dike in Cleveland more of them amongst the subcalcareous portions of the Inferior Oolite, as at Boltby and especially where in the Howardian tract the calcareous character of the interposed band is most clearly marked. Some of the commonest of the Subxerophilous species are scattered at intervals over the sandier parts of the Central Valley and may be found in such stations as the Ouse side along the Clifton Ings, the banks of the Swale at Topcliffe, of the Tees between Stapleton and Croft and the gravelly soils of the neighbourhood of Bedale and Kirklington. M. Thurmann gives for the portion of Central Europe which includes the Vosges and the Jura both a list of the indigenous plants and an account of their distribution with regard to the subjacent rocks. Comparing the British flora as a whole with that of this region or indeed with that of any other part of the interior of Central or Southern Europe we see even by glancing over the mere list of names how conspicuously with us the damp-loving element predominates. When a British and Foreign Cybele is written, a work giving an account of the distribution of British plants through foreign countries and of the relation. of our indigenous flora to that of Europe as a whole, this is one of the points which its author will have to explain to us and illustrate for us in detail. Out of fifty species which M. Thurmann gives as being within his limits the commonest plants which are characteristic of dysgeogenous tracts we have in North Yorkshire as indigenous plants eight species only out of the fifty species which he names as the commonest plants which are characteristic of the eugeogenous tracts within his limits we have in North Yorkshire thirty-one species. With us several of the most characteristically paludal plants. which are common in the neighbourhood of York and Thirsk are altogether confined to the vales and nowhere ascend into the dales or amongst the lower levels of the hill-slopes. This is the case with Thalictrum flavum, Nymphæa alba, Nasturtium amphibium, Cerastium aquaticum, Utricularia vulgaris, Hottonia, Hydrocharis, Sagittaria, Butomus, Potamogeton densus, Lemna trisulca and several other species. In Central Europe we have, as in North Yorkshire, ranges of hills of well-marked contrasting lithological character, the Jura dysgeogenous and the Vosges and Black Forest eugeogenous. The following are the thirty-one species which inhabit North Yorkshire which are given by M. Thurmann as characteristically eugeogenous. These are plants which ascend and are frequent amongst the eugeogenous Vosges and Black Forest but are either rare amongst or altogether absent from the dysgeogenous Jura, under parallel or nearly parallel conditions of atmospheric climate. LIST OF NORTH YORKSHIRE PLANTS WHICH ARE We see that we have in this list most or very nearly all the very species which make up the gregarious swamp-heatherland vegetation of which we have spoken as covering in our country. such wide tracts of surface. These species are several of them our commonest North Yorkshire plants and ascend amongst |