SUMMARY. 361 



To sum lip: of M. Thiirmann's three categories of Mid-Europe species, 

 there are in Middlesex : — 



per cent. 

 XerophilouB . . . 19-20 (29 out of 149) 



Psammophilous . . . 53-65 (44 out of 82) 



Pelophilous . . . 61-53 {24 out of 39) 



On examining the lists of Middlesex species which we have given, 

 it will, however, be seen that their relationship to the subjacent rocks 

 here is by no means in every case similar to that which obtains in Central 

 Europe. 



Let us first look at the lists of xerophilous species. Out of the 29 species 

 there enumerated not more than 9, i. e. the first 2 of the former list and 

 the first 7 of the latter, are with us restricted to the calcareous district ; 

 the remaining 20 are by no means confined to the chalk of the county, 

 though a few of them show more or less partiality for it. We have, 

 however, some other species, whose range seems confined to our chalk dis- 

 tricts : — 



Dentaria bulbifera. Specularia hybrida. 



Reseda lutea. Gentiana Amarella. 



Viola hirta. Chlora perfoliata ? 



Onobrychis sativa. Neottia Nidus-avis. 



Bupleurum rotundifolium. Bromus erectus. 



Campanula Trachelium ? Triticum caninum. 



These, which all occur in the Jura, are not considered xerophilous in 

 Thurmann's ' Essai.' 



In the list of psammophilous species also the majority do not show a 

 decided bias for any soil. The first 16 names, however, are well-marked 

 sand and gravel species in Middlesex, and to these may be added as equally 

 characteristic (though not so in Central Europe) the following 9 (making 

 ■with the others 25) : — 



Lepidium Smithii. Trifolium striatum. 



Viola canina. Erigeron canadensis. 



Sagina ciliata. Plantago Coronopus. 



Moenchia erecta. Carex panicea. 

 XJlex nanus. 



Analogous remarks may be made with regard to the third category, that 

 ot pelophilous species. Only the first 7 names in the list are well-marked 

 clay plants in our county, the remainder being more nearly sand-loving 

 species here, and two {Specularia and Chlora) confined to the chalk. The 

 following species may be added to the 7 to make up 25 characteristic 

 'pelophilcs' in Middlesex for comparison with the ' psammopkiks ' 

 above : — 



Hypericum hirsutum. Genista tinctoria. 



Rhamnus f rangula. Lathyrus macrorrhizus. 



