CENSUS OF SPECIES. 277 



S. South Britain includes subprovinces 1 to 19. 

 N. North (and Mid) Britain „ 20 to 38. 



The second or treble column, with the head letters W Sc E, shows the 

 number of subprovinces for Scotland in contrast against England, and the 

 western and eastern sides of England also in contrast against each other. 

 It was of course impossible to divide the 25 English subprovinces into 

 two groups exactly equal with the 13 Scottish subprovinces; and the 

 western division has accordingly only 12 instead of 13. The chief 

 purpose of this second column of figures, is to form such a comparison 

 or contrast as will bring into view any peculiar tendency of particular 

 species to the western or to the eastern side of the island. For this 

 purpose it was found that the two sides of England, apart from Scotland, 

 were more suitable than the two sides of total Britain ; their division 

 being imperfect and unsatisfactory in North Britain, and the distinction 

 between eastern and western species being there confused by the 

 intermingling of alpine or arctic plants with them. And by placing 

 the nos. for the Scottish subprovinces between the two series for 

 England, a second comparison of South with North is also obtained, 

 less unequal than the former in respect to latitude. The line of separa- 

 tion between the western and eastern divisions was explained on pages 

 136 — 7 of the present volume. On comparing eastern and western 

 England together, or these two with Scotland, it will be very evident 

 that difference of latitude is far more potential than difference of longi- 

 tude, in altering the distribution of plants. The floras of western and 

 eastern England are more closely similar than those of England and 

 Scothind ; and there is correspondingly a less diversity in the sub- 

 provincial census of the species, that is, less between west and east in 

 England, than between either of these and Scotland. 



But slight differences in the stated number of subprovinces may be 

 disregarded, especially in the ternary division where the totals are only 

 12 and 13. The lists of species for several of the subprovinces being 

 incomplete, their numbers may be rendered unequal for some of the 

 species simply through deficiency of knowledge. Tbus, Jttncvs effusus 

 is represented as wanting in one of the northern and Scottish sub- 

 provinces, on account of the name not appearing in Balfour and Ba- 

 bington's list of species observed in the Hebrides. The presumption, 

 however, is very strong in this instance, tliat the name of Juucus conglo- 

 tneratiis was incorrectly substituted in their list, or that it really included 

 both the species. See volume third, page 39 of this work, for the 



