20 INTRODUCTION. 
appearance of Convolvulus sepium, Bryonia dioica, Tamus com- 
munis, Acer campestre, Rhamnus catharticus, Ulex nanus, Vibur- 
num Lantana, Euonymus europaeus, and Cornus sanguinea ; all 
of which occur also in the lowest zone, and more plentifully there ; 
while none of them are ascertained to occur truly native in the 
uppermost portion of the Agrarian region; and all certainly 
fail far below the upper limit of Pteris aquilina ov of cultivated 
crops. 
The Infer-agrarian zone will embrace all the country southward 
from the Dee and Humber (continued into the river Trent) ex- 
cepting the mountainous tracts of Wales and the higher hills and 
moors in the provinces of the Severn and the Peninsula. This 
zone is more particularly characterised by the increased prevalence 
of the species before mentioned as commencing in the zone above. 
Clematis Vitalba is one of the couspicuous species almost (if uot 
quite) restricted to this zone as a truly native shrub. Rubia pere- 
grina is another characteristic species, partially prevalent in the 
southern and western counties; while the Clematis affects the 
calcareous tracts of the southern, eastern and inland counties, 
where it is often abundaut and conspicuous. ‘hough several 
species are quite peculiar to this lowest, or most southern, of the 
six zones, they are usually too scarce or too local to be relied upon 
as characteristic tests. Examples occur in Erica ciliaris, Iilece- 
brum verticillatum, Sibthorpia europaea, Cyperus longus, Scilla 
autumnalis, Pulicaria vulgaris, and Actinocarpus Damasonium. 
The six climatic zones, into which the two regivus are thus 
subdivided, may be better understood and borne iu meniory, 
after presentation to the eye in closer connexion with each 
other. Their Nos. are reversed here because it has been found 
more convenient to describe or explain the zones downwards, 
although the plants themselves are in general traced niore 
readily upwards, that is, from south to north, from low to high 
grounds, from the open country to the montane valleys and 
acclivities :— y 
