222 Quantitative Analysis of Plant Growth 



linear basis, L x being the leaf-area at the beginning of the week, and 



L 2 at the end of the week. 



Unit leaf-rate, E, is the rate of increase in dry-weight per unit leaf- 



dW 

 area per week. Then -=- = EL and if the exponential basis be adopted 



for both leaf-area and dry-weight increase then 



w — w 



w — w 



On the linear basis E = —^ sr-= , that is, the weekly increase in dry- 



2 

 weight divided by the average leaf-area. 



Relative leaf growth -rate, R L , is analogous to relative growth-rate and 



1^= log. ^- log. A, or 2 4^, 



2 

 according to whether the calculations assume an increase on the ex- 

 ponential or the linear basis. 



An inspection of the above definitions and formulae will show that 

 whichever formal conception as to the mode of increase of dry-weight 

 and leaf-area be adopted the Relative Growth Rate is merely the product 

 of the Leaf -area Ratio and the Unit Leaf Rate multiplied by 100. This will 

 be made clear by the following. On the exponential basis 

 dW dW 



R=lOo4}r, -4 = 4, and E = ■$- , hence R = 100AJB. 

 W W L 



On the linear basis it will be seen that the same relationship holds. 



In the present and the previous chapter the linear basis has been 

 adopted as the simpler one, and as being sufficiently accurate for the 

 purposes. 



None of the above formulae involves the assumption that R, R L , A y 

 or E are constant throughout the life-cycle. 



LITERATURE CITED. 



(1) Boysen- Jensen, P. Studies on the Production of Matter in Light- and Shadow- 



Plants. Bot. Tidsshr. xxxvi, Heft 4, 1918, p. 219. 



(2) Blackman, F. F. and Matthaei, G. L. C. Experimental Researches in Vegetable 



Assimilation and Respiration. IV. A Quantitative Study of Carbon-Dioxide 

 Assimilation and Leaf-Temperature in Natural Illumination. Proc. Boy. 

 Soc. (Lond.), B, lxxvi, 1905, p. 402. 



