126 S. MINVER AND BRADFORD ABBAS PLANTS. 



Dorsetshire, and at S. Minver, in Cornwall. They are widely 

 separated from each other, and differ essentially in their 

 geological features. Bradford is on the Inferior Oolite and 

 Fuller's Earth, S. Minver is on the Devonian, with eruptive 

 volcanic rocks interspersed. It differs, too, in having a seaboard 

 and some heath land, also in a climate favourable to such 

 southern types as Diplotaxis mtiralis, Fumaria pallidiflora, 

 Medicago denticulata, and Lotus angusti'ssimus, which, although 

 not maritime on the Continent, require a mean temperature such 

 as that which exists only on the southern coasts of England. 

 The influence which proximity to the sea exercises in reducing 

 the difference between summer and winter is very remarkable. 

 In Edinburgh it is 19*1, in York 23^4, in Leeds 20'8, in 

 Greenwich 22-3, Exeter 19-3. Mr. H. C. Watson gives, the 

 mean annual temperature of the coast of Cornwall to be 52, 

 that of the south coast of Devonshire 5 1, and of Dorsetshire 51. 

 The geology of a district influences its flora equally with the 

 climate, soils differ in their power of retaining or absorbing 

 moisture, calcareous rocks do not disintegrate freely, and resist 

 the abrading atmospheric influences ; the most absorbent of all 

 are those in which the argillaceous element predominates. If 

 we take a quantity of dry sand, and pour water upon it, we shall 

 find that it will not absorb more than a quarter of its own weight 

 of the water, but vegetable loam will absorb 40 or 50 per cent, 

 of its own weight, and dry argillaceous clay will absorb as much 

 as 60 or 70 per cent. Argillaceous soils are comparatively humid 

 and cold, and in dry weather become hardened and form a crust 

 on the surface. Arenaceous soils, on the other hand, are often 

 light and sterile, and in dry weather become parched. Under 

 equal climates and at equal elevations the argillaceous soil has a 

 more humid and boreal vegetation. 



Number of plants common to both districts - 284 



,, ,, found at S. Minver only - 138 



Maritime plants, S. Minver - 32 



found at Bradford Abbas only - 144 



