RAUNKIAER'S "LIFE FORMS," "LEAF-SIZE CLASSES," 

 AND STATISTICAL METHODS 



GEORGE D. FULLER 

 University of Chicago, Chicago, Illinois 



AND 



A. L. BAKKE 

 Iowa Stale College, Aynes, Iowa 



III. SUMMARY OF THE VALENCE METHOD^ 



1. The valeiice method offers an objective means of investi- 

 gating a plant formation by differentiating its species according 

 to their frequency expressed numerically so as to serve both as a 

 means of direct comparison of closely related formations and also 

 as a basis for an indirect comparison by passing from systematic 

 units (species) to units of another sort; viz., ecological or phys- 

 iognomical, and thus permitting an exact comparison between 

 formations which are floristically entirely different from one 

 another, 



2. For the ecological characterization of a formation the fre- 

 quency of the occurrence and the growth habits of a species are 

 the outstanding things, while physiognomical characterization is 

 essentially dependent upon the aspect (mass condition) of the 

 vegetation as a whole (in connection with frequency). 



A. Frequency^ 



3. Frequency is determined bj' taking a number of sample 

 areas of a certain size and expressing numerically, in terms of 

 percent, the number of these samples in which the species in 

 question occurs: Frequency percentage (F%). 



3 Raunkiaer, C., Om Valensmetoden. Bot. Tids. 34: 304-311. 1917. 

 * Raunkiaer, C., Measuring apparatus for statistical investigations of plant 

 formations. Bot. Tidsskr. 33: 45-48. 1912. 



57 



THE PLANT WORLD, VOL. 21, NO. 3 

 MARCH, 1918 



