NORTHTJMBEKLAiS[D AND DtrKHAM. 43 



in saying, 1. — The species wliicli in Central Europe are restricted 

 to dysgeogenous tracts occur with us in small number only, and 

 are restricted lithologically in a similar manner. 2. — The species 

 which in Central Europe are restricted to eugeogenous tracts 

 occur with us in large number ; and under our more boreal and 

 humid climate grow abundantly, and cover wide areas of surface 

 without keeping up any clearly -marked role of lithological re- 

 striction. And this shows us in what direction the interference 

 of the rocks operates. A more porous and more humid soil evi- 

 dently, to some extent, compensates for a drier climate ; and in 

 proportion as the climate is damper the characteristically dry- 

 loving species are more restricted to dry-soiled tracts of country. 

 This is the rule, and in botanico-geographical considerations it is 

 evidently worth bearing in mind ; but to what extent it has been 

 influential in determining which species we should have or which 

 we should not have, either in our two counties or in Britain as a 

 whole, or to what extent it has, for instance, operated in the 

 restriction to the area which they occupy, of the plants of what 

 Mr. "Watson calls the Germanic type of distribution, we can but 

 guess vaguely. 



About the basalt and porphyry we have said nothing as yet. 

 The following is a type florula for one of our lower zone porphy- 

 ritic crags, the cliff selected being one by the side of the Coquet, 

 between Windyhaugh and Shillmoor, at an elevation above sea- 

 level of from 630 to 700 feet. 



Florula of a Lower Zone Porphyritic Crag. 



Draba verna. 

 *Ai*abis hii'siita. 



Sisymbmun thalianum. 

 *Heliantheraum viJgarc. 



Dianthus deltoides. 



Cerastium triviale. 



Sagina procumbens. 



Viola sylvatica. 



Gei'aninm Robertianum. 



Hj-pericum pulchrum. 



Spartium scoparinm. 



Rosa spinosissima. 

 Pimpinella saxifraga. 

 Hedera helix. 

 Galium cruciatiuii. 



verum. 

 * sylvestre. 



Hieracium pilosella. 



viilgatum. 

 Leontodon taraxacum. 

 Apargia autumnalis. 

 Carduus lanceolatus. 



