240 baker's north YORKSHIRE. 



shore which the West has not. The other species not common 

 to both are not more specially damp-loving in one case than the 

 other. 



The influence upon the topography of our flora in respect of 

 humidity exercised by the distribution of the subjacent rocks is 

 considerable, but it is not needful to recapitulate or summarise 

 here what has already been advanced upon this head. For what 

 I have to say upon the matter the reader is referred to the chapter 

 on Lithology. 



Expla7iation of the Manner of Stating the Distribution of Species. 

 — We may claim as plants of North Yorkshire very nearly three 

 out of every four of the species which inhabit the whole of 

 Britain. This proportion applies both as regards the Flowering 

 Plants and Ferns, and also to the Mosses. In our list of species 

 the fourth volume of the Cybele Britannica has been followed 

 as a standard of nomenclature and arrangement, and what are 

 there given as species are here given as species, with very trifling 

 alteration. Occasionally, as in the case of Callitriche verna and C. 

 platycarpa, I do not possess the materials for tracing out properly 

 the distribution of two closely allied plants as distinct from one 

 another, and have united them for this reason. I have not 

 thought it necessary to take up space by giving the names of 

 the Natural Orders. Under each species its type of distribution 

 for Britain as a whole is given. These types were first worked 

 out by Mr. H. C. Watson,* and are as follows : — ■ 



1. British type. — Species which are more or less generally 

 diffused throughout the whole or nearly the whole of Britain. 



2. English type. — Species which have their head-quarters in 

 England, especially in the southern provinces, and become rare 

 and finally cease altogether towards the north. 



"■ The classification of species iinder their types of distribution as given by Mr. Watson 

 in the fourth volume of the Cybele (pp. 175 — 221) has been followed implicitly; I have 

 given here only the primary type to which each species is referred, but in the list in the 

 Cybele the normal representatives of each type are distinguished from the species which 

 are less characteristic. 



