42 



GEOGKAPHICAL DISTRIBUTION. 



the forms characteristic of the present Intermediate Flora should therefore be largely of 



the natural conditions to which they have been subjected 



Circumpolar type. As, however, 



such as pass into those favourable for an ad 



of the Equatorial Flora, a tendency 



to the zonal distribution characteristic of an advancing flora has been imparted to it 



Briefly 



tated 



the condition of affairs has alway 



b 



th 



the constituents of the 



each 



Intermediate Flora during 



derivates of the flora that retreated during 



distribution parallel to the constituents of th 



period of approximate equilibrium h 



been 



inly 



the migration immediately preced 

 flora that advanced 



3 



in 



during th 



same time 



The general agreement of the distribution of Pedicularis with this hypothesis becomes 

 very evident when table VI given above (p. 25) is replaced by a diagram in which the 



endemic percenta 



shown 



DIAGEAM 2». 



Endemic percentages 



24 sp. 



America. 



87i°/ En. 







1 If the hypothesis be correct, the forms characteristic of the Southern Intermediate Flora should eridence their residual 

 character by being of Equatorial type, and as physiographical circumstances have protected them from pressure on the part of 

 an advancing southern Circumpolar Flora during the most recent migration, their forms should exhibit a meridional rather 

 than a zonal distribution. We should expect, for instance, to find in South Africa that lateral distribution ~e.g. the 

 ppearance of the same species in Western Cape Colony and in Natal — is a somewhat exceptional phenomenon. This does 

 not, however, affect the constitution of the genus under discussion. 



This diagram and the nine that succeed it are uniform and have been constructed on the following principle : — The 

 centre of the circle that represents the Arctic province coincides with the North Pole, while the centre of each of the other 

 circle* coincides with the centre of area on a map of the Northern Hemisphere of each of the individual provinces ; the area 

 of each circle is at the same time in direct proportion to the total number of species of Pedicularis reported from the 



province that the circle represents— an arbitrary area being of course chosen for one province, the others being made to 

 conform to the first* 



* 



