100 UEPORT — 1855. 



superficial detritus, which may be either of a sandy or clayey nature. They are 

 comparatively impermeable, and consequently hygroscopic upon a grand scale, fur- 

 nishing damper stations than the roclis of the opposite category, especially when 

 the detritus is clayey. 



5. Every species possesses essentially its characteristic special range of lithological 

 adaptability, in the same way that each possesses its characteristic special range of 

 climatic adaptability. Under equal climatic conditions some species are restricted 

 to more or less distinctly marked dysgeogenous situations, and others to more or 

 less distinctly marked eugeogenous situations ; but a greater number can adapt 

 themselves more or less decidedly to stations of either class. 



6. In proportion as we advance from an austral to a boreal, and from a conti- 

 nental to an insular climate, the proportion in number which the restricted (i. e. 

 dysgeogenous and eugeogenous) bear to the ubiquitous species lessens, principally 

 through reason of many of the eugeogenous species being able, under more humid 

 conditions of climate, to adapt themselves also to dysgeogenous situations. 



II. The Field of Study Uthologicalhj viewed. — For phytostatic purposes the surface 

 of Britain may be conveniently considered as subdivided into six lithological 

 zones, viz. — 1. Psammo-eugeoyenous ; including the endogenous and metaraorphic 

 rocks of the Scotch Highlands and sedimentary strata that surrounds them. 



2. Mixed : including the Silurian and Devonian, and accompanying strata of the 

 southern part of Scotland and of Wales and the West of England. 



3. Primary dysyeoyenous : including the carboniferous formations of the Penine 

 chain and Permian limestones, enclosing the coal-fields of Durham and West 

 Yorkshire. 



4. Eugeogenous : including the New Red Sandstone strata of the centre of En- 

 gland. 



5. Secondary dysgeogenous : including the liassic, oolitic, Wealden and cretaceous 

 strata of the south-eastern half of England. 



6. Subeugeogenous : including the fen country and London and Hampshire tertiary 

 basins. These are almost all occasionally interrupted by intervals of less typical or 

 exceptional nature. 



III. Summary of Species. — 



Class. No. of Species. Per-centage. 



A. Dysgeogenous 92 7 + 



AB. Subdysgeogenous 75 6 — 



B. Ubiquitous 699 53-f- 



CB. Subeugeogenous 89 7 — 



Cl. Eugeogenous, austral 65 5 — 



C2. ' „ boreal 79 6 + 



D. Maritime 90 7— 



E. Hibernian and Sarnian 37 3 — 



F. Local or dubious 89 7 — 



1315 



Oh Galium montanum, Thuill. and G. commutatum, Jord. 

 By John G. Baker. 

 The author announced the discovery in Yorkshire of these two continental species, 

 and pointed out their distinctive characters. 



ExJdbition of a Series of Specimens illustrating the Distribution of Plants in 

 Great Britain f and Remarks on the Flora of Scotland. Z?y Professor 

 Balfour, M.D., F.R.S.E. 



After making some general remarks on the geographical distribution of plants, 

 and calling attention to the important addition made by Drs. Hooker and Thomson, 

 Mr. Spruce and other botanical travellers. Dr. Balfour proceeded to the consideration 

 of the British Flora. He noticed the important services rendered by Mr. Watson, 

 and illustrated the flora of the British Isles by means of specimens arranged on 

 large sheets of paper in a map-like manner, so as at once to suggest the prevalent 

 forms of plants in different districts. 



