PROCEEDINGS OF 



THE EOYAL SOCIETY. 



Section B. — Biological Sciences. 



Experimental Researches on Vegetable Assimilation and Respira- 

 tion* V. — A Critical Examination of Sachs' Method for 

 using Increase of Dry Weight as a Measure of Carlton 

 Dioxide Assimilatioii in Leaves. 



By D. Thoday, M.A., Mackinnon Student of the Eoyal Society, late 

 Frank Smart Student of the University of Cambridge. 



(Communicated by Dr. F. F. Blackman, F.R.S. Received June 11, — Read 



June 24, 1909.) 



CONTENTS. 



PAGE 



Section I. — Introduction 1 



,, II. — On the Nature of the Errors to which the Half-leaf Dry- 

 Weight Method is Liable 3 



„ III. — On Changes of Composition during Insolation 4 



„ IV. — The Error from Lack of Symmetry 12 



„ V. — The Error from Change of Area during Experiment' 19 



,, VI. — On the Measurement of Area 39 



„ VII. — On the Killing and Drying of Leaf Material 45 



„ VIII. — General Considerations on the Degree of Accuracy and the 



Utility of the Method 48 



„ IX. — Conclusions 53 



Section I. — Introduction. 



The trustworthiness of Sachs' well-known dry - weight methodf for 

 measuring the rate of accumulation and translocation of the products of 



* Earlier contributions to this series of investigations carried out under the general 

 direction of Dr. F. F. Blackman at Cambridge are the following : I and II, Blackman, 

 ' Phil. Trans.,' B, 1895 ; III, Matthaei, ' Phil. Trans.,' B, 1904 ; and IV, Blackman and 

 Matthaei, ' Eoy. Soc. Proc.,' B, 1905. 



t Sachs, Julius von, " Ein Beitrag zur Kenntuiss der Ernahrungsthatigkeit der Blatter," 

 ' Arbeit, d. Bot. Inst, in Wiirzburg,' III, 1883, p. 19. 



VOL. LXXXII. — B. B 



