THE BISECT. 



433 



and the consequent effect upon the course of succession. There is no question 

 that investigations of this sort must become increasingly frequent in the study 

 of development, and that the bisect will become a regular method of investi- 

 gation and record (c/. Weaver, 1915, 1916). 

 4ftr 

 k 



Fig. 49. — ^Bisect of sandhills mixed association in eastern Colo- 

 rado, a, CalamovUfa longifolia; h, Artemisia filifolia; e, An- 

 dropogon scopanus; d, A. hallii; e, Ipomoea leptophyUa; 

 f, Aristida purpurea; g. Boutdoua hirsuta. After Shantz. 



FiG. 50. — Bisect of the Bulhilis-Bouteloua-poion in eastern Colo- 

 rado, a, Bovteloua oligostachya; b, BulbUis dactyloides. 

 After Shantz. 



The migration circle.— The migration circle (Clements, 1905: 182; 1907:212), 

 or migrarc, is designed to make possible the exact analysis of migration, es- 

 pecially without reference to ecesis. Practically all studies of migration have 



