10 INTBODUCTKXN. 



mixed with smaller plants, is the only fuel."* The 

 flowers of this heath are white, rose-coloured, or light 

 purple, producing a very pretty effect. 



The serpentine, at least in Britain, produces several 

 rare plants not to be found elsewhere, one of which is 

 the fringed Rupture-Wort (Herniaria ylabra), hence 

 the Lizard district, in Cornwall, is one of the most 

 interesting localities that can be visited by a student 

 in British botany. The Red Broom-rape (Orobanclie 

 rubra), is another rare plant, which, though parasi- 

 tical on the roots of broom, furze, clover, &c., yet, by 

 some unaccountable affinity, is only found on basaltic 

 rocks. It occurs on the cliffs of Kynance, Cornwall, 

 on the Giant's Causeway, and at Staffa. 



Gravelly commons possess several plants that occur 

 also upon trap-rocks, and their general productions, 

 such as minute Clovers (Trifolium repens, fragiferum, 

 minus, andjiliforme), OrnitJiopus perpusillus, Plantago 

 coronopus, &c., will be much the same, whether the 

 gravel be granitic, diluvial, or tertiary. Thus the 

 vegetation on the primitive gravel of the extensive 

 green spreads of "Welland Common, and others at 

 the base of the Malvern Hills, in Worcestershire, is 

 repeated on. Ealing Common, and other waste spots in 

 Middlesex, even to the Chamomile (AntJiemis noUlis), 

 and the rarer Bupleurum tenuissimum. Much will 

 depend, however, upon the presence or absence of 

 water, in pools or minute rills. If the former present 

 themselves, the species of CallitricJie, Myosotis, and 

 Widens, are sure to occur, and Ranunculus sceleratus 

 and Pulicaria vulgaris will be conspicuous plants. 

 Little prills and marish spots will nurse such species 



* A Week at the Lizard, by the Rev. C. A. JOHNS, p. 269. 



