284 Matthews.—The Distribution of certain 
‘ English ’ species survived the Glacial Period in Britain. Some certainly 
existed in the country during the Pliocene, being recorded either from the 
Cromerian or from the Castle PIden floras. These are Acer campestre , L., 
Inula Conyza , DC., Picris hieracioides , L., Carpinus Betulus , L., Fagus 
sylvatica , L., Stratiotes aloidcs , L., Naias marina , L., and Potamogeton 
trichoides , C. and S. Others may be regarded as allied in their distribution 
to that Atlantic element in our flora which is considered by some as of 
pre-glacial age in Britain. These are Arabis stricta, Huds., Hypericum 
undulatum , Schousb., //. linariifolium , Vahl., Physospermum cornubiense , 
DC., Cnicus tuberosus , L., Lobelia urens , L., F.rica ciliaris , L., A. vagans , 
L., and Scrophidaria Scorodonia , L. There is no evidence of the occurrence 
of any of these western plants in glacial deposits. Their survival would 
mean long occupation of the country, yet they have not spread far during 
the long interval since glaciation, nor, as has been pointed out by Seward 
( 1911 ) for the Lusitanian species occurring in Ireland, have they evolved 
new forms as might be expected of species of antiquity and long 
isolation. 
If we turn to the ‘ Age and Area ’ hypothesis we should interpret this 
restricted English flora as recent. The species which comprise it should, 
on the average, be among the last to have arrived. If most of them have 
advanced by way of France and spread no farther than the southern 
counties of England, it is because they are still comparatively young in the 
country. 
This idea embodied in the ‘ Age and Area ’ theory is by no means new, 
as Willis himself points out in his recent volume on the subject, and it is 
interesting to find that in 1913, two years before Willis published his theory, 
Clement Reid had written, ‘ A hardy fauna and flora seem to characterize 
the period of the submerged forests [of Britain] ; but the absence or great 
scarcity of characteristic survivors from a former period suggests that even 
the lowest of these deposits is far removed from the Glacial Period. The 
arctic species had already had time to die out or had been crowded out; 
bid the time had not been sufficiently long for the incoming of the southern 
forms ivhich now characterize our southern counties' (italics mine). The 
idea that the southern species occupying the south of England are recent 
arrivals is here clearly expressed. 
It is on much statistical evidence, however, that Willis bases his theory, 
and an examination of Diagram 1 clearly suggests that numerous species 
occupy a comparatively small number of counties to produce the con¬ 
centration in the south-east, and, in contrast to this, few species are so 
widely dispersed as to occupy all the vice-counties of the country, seventy- 
one in number. Working out the details and arranging the species in ten 
classes representing varying degrees of rarity, we obtain the results shown 
in Table I. 
