348 The Ohio Naturalist. [Vol. VIII, No. 7, 



considerable interest as showing that by the use of the quanti- 

 tative method we are passing to an equally definite and exact 

 determination of the importance of environmental conditions. 

 The points brought out in this communication may be sum- 

 marized thus: 



(1) The data above presented show clearly that a biomet- 

 ric record of secondary growth in trees furnishes a very valuable 

 criterion for the comparison of the conditions of different plant 

 habitats. They are data involving climatic and edaphic factors 

 which are of the greatest importance to plant life, and hence 

 may be best correlated with functional and structural changes. 



(2) The response to environment in the case of Acer rubrum 

 is rapid and pronounced. The annual growth of wood auto- 

 matically records in duration, intensity and quality the effect 

 of the "various ecological factors working in concert" (3). 

 The differences in amount and size of wood cells, in thickness 

 of walls, extent of infiltration, etc., clearly indicates differences 

 in type. 



(3) In a study such as this the biometric data seem more 

 valuable than long records of temperature, light, humidity,. 

 wind velocity, and others. The effect of these is included as 

 far as they influence the plant. Greatly varying as meteorolo- 

 gical and soil data are, it is indeed almost impossible to combine 

 them so as to exhibit their united action to climatic and edaphic 

 centers of development. Hence the biometric point of view is 

 an additional criterion to furnish a suitable basis for comparing 

 ecological data, and for determining the relation of a locality 

 to the whole range of the species, and to the direction of its mi- 

 gration (1). It seems certain, therefore, that if such statis- 

 tical data were exhibited for various regions, climatic and edaphic 

 centers of distribution could be clearly indicated (9). It is 

 hoped that investigators in other places will make studies sim- 

 ilar to the one here presented for the purpose of testing the value 

 of this criterion. 



(4) It is well known that the ability of plants to transmit 

 acquired characteristics is readily demonstrated in forest trees^ 

 where climatic influences continue to show themselves with 

 plants grown from seed derived from different localities. It 

 becomes a problem of practical as well as theoretical import- 

 ance to determine to what extent such distributions in functional 

 variations persist. The advantage of the biometric method 

 to know definitely the behavior of plants and the effect of en- 

 vironment is apparent. Whether or not individuals which 

 have proven to be more variable would be favorable to any 

 selection process remains to be seen from experimental deter- 

 minations. 



Botanical Laboratory, O. S. U. March, 1908. 



