293 
Portions of the British Flora. I. 
Table II or Diagrams 4 and 6 will show. These two series of figures may 
well suggest the questions whether the two assemblages of plants to which 
they refer are concentrated in areas where they arrived and became estab¬ 
lished, or whether they constitute residual groups squeezed into these 
corners by a process of elimination and disintegration which has been more 
than remarkably regular. From the former point of view distinct invasions 
are suggested, although it need nofc be supposed that every species occurring 
in the Channel province, for instance, arrived there by direct migration. 
Common species may occasionally have followed a more circuitous route, 
arriving, perhaps, by way of the Peninsula or by way of the Thames area. 
Attention may next be drawn to an interesting and important feature 
exhibited by Diagrams 3-6 taken consecutively. The concentration of 
species in the several districts in England is very fairly matched by the 
European distribution. The centre of dispersal for the Ouse group is 
Germany and France, but for the Peninsula assemblage it swings round to 
France and Spain. In their most general features the maps correspond 
with those of Stapf ( 1916 ), who worked with the southern element of the 
British flora as determined by its range on the Continent, whereas I have 
worked with a group whose boundaries are determined by its range in 
Britain. 
The results so far obtained, indicative of the distribution of the rarest 
species in England, seem consistent with the general principle of ‘ Age and 
Area ’. It is of importance, therefore, to test the question further by 
analysing the data for all the English species. Of the total number (266), 
only 33 are absent from the four provinces we have been considering, 
i. e. three in addition to the thirty of the rarest class. The dispersal of the 
remaining 233 through these four areas may be seen from the figures given 
in Table III. 
Table III. 
Ouse. 
Thatnes. 
Channel. 
Peninsula. 
142 
108 
IOI 
63 
108 
144 
116 
73 
IOI 
116 
157 
89 
63 
73 
89 
117 
These figures confirm the results obtained from the smaller numbers 
dealt with in Table II. They also serve to illustrate the general features 
already expressed cartographically in Diagram 1, where it is shown that the 
‘ English ’ flora, taken as a whole, is most abundant from Norfolk to Dorset. 
The Channel province is now seen to possess the largest number of species. 
It is through this area that the bulk of our English flora may be regarded 
as having advanced from the Continent, although we ha\e seen that other 
movements west and north have played a part in the building up of 
the flora. 
