202 Leaf-Product [400 



LEAF-PRODUCT AS AN INDEX OF GROWTH IN 

 SOY-BEAN 



By F. MERRILL HILDEBRANDT 



It has been pointed out by McLean x that the sum of the 

 products of the length and breadth of all the leaflets on a 

 soy-bean plant 4 weeks old is approximately proportional to 

 the total leaf area of that plant,, and he adds that the leaf 

 area is itself nearly proportional to the total dry weight of 

 stem and leaves. The sum just mentioned has been called 

 the leaf-product by the same writer, his observations being 

 based on measurements obtained at two stations in Maryland, 

 Easton and Oakland, in the project carried out during the 

 summer of 1914 by the Maryland State Weather Service in 

 co-operation with the Laboratory of Plant Physiology of the 

 Johns Hopkins University. That project included similar 

 studies of the relation of plant growth to climatic conditions 

 at seven other stations in Maryland, besides Easton and Oak- 

 land, and the present paper aims to bring out the fact that 

 this interesting relation between leaf-product, leaf area and 

 dry yield of tops applies generally to the soy-bean data for 

 all nine stations. 



If the method proposed by Livingston 2 and McLean, of 

 employing the growth rates of standard plants as indices for 

 the comparison of different climates as these influence plant 

 growth in general, is to be of value, it is of course necessary 

 that suitable plant characteristics be chosen for measurement 

 in determining the growth rates, and it is desirable that the 

 measurements be such as may be made from time to time 

 without injury to the plants. The most generally accepted 



1 McLean, F. T., "A preliminary study of climatic conditions in 

 Maryland, as related to plant growth." Physiol. Res. 2: 129-208. 

 1917. 



2 Livingston, B. E., and McLean, F. T., "A living climatological 

 instrument." Science, n. s. 43: 362-363. 1916. 



