106 POSITION OF AGE AND AREA THEORY [pt. ii, ch. x 



neither premeditated nor foreseen. Just as a river wearing its 

 way into a mountain-jnass unites in a single system widely 

 separated streams by capturing one water-head after another, 

 so the Age and Area theory in its advance is bringing about the 

 coalescence of principles that we have been wont to consider as 

 things apart. 



This may be the luck of the trail. But at all events we have 

 to distinguish between the direct and indirect results, and one 

 scarcely knows which will prove to be the most important out- 

 come of this investigation. It is difficult to speak of work still 

 on the stocks, but we will expect to find in the results of the 

 tabulation of the genera of the flowering plants a survey of the 

 distribution of some 12,000 genera over the great regions of the 

 globe, Endemism will figure more as a world-affair than as a 

 peculiarity of localities, and some unexpected results are to be 

 looked for in a treatment of endemism in the mass. Then there 

 will be the story of the monotypic genera that appropriate 

 almost two-fifths of the total of the genera of the flowering plants ; 

 and their part in the forming of the curve of all the genera 

 grouped by the number of their species will prove to be a 

 triumph for the mutationists, A closing word may be said of 

 the great labour involved in the preparation of the tabulated 

 results, of the weeks of counting to establish a single point, and 

 of the wearisome recovering of the ground to make some doubtful 

 point assured. Since it was the purpose of the writer to place 

 rather than describe the Age and Area theory more cannot be 

 said here. 



