XXVI 



INTRODUCTION. 



admitted into the work in the same way as the three otliers. Of the 817 

 Plymouth species the five following are probably extinct, as they have 

 not been seen for many years past : 



Nasturtmm palustre. 

 Vicla hithynica. 

 Comarum palustre. 

 Veronica Anagallis. 

 Eiqyhorbia plati/phylla. 



The 877 species are divided as follows, with reference strictly to the 



area : 



Natives . . . . . 72.S 



Denizens 

 Colonists 

 Aliens 

 Casuals 



48 

 48 

 37 

 16 



877 



As regards their relative frequency they stand as follows ; but of course 

 there are some species which might be placed almost indifferently in 

 either one or another of the lists : 



764 



The 113 remaining plants are Segregates, Introductions, &c., not 

 classified by Watson. 



