Researches on Vegetable Assimilation and Respiration. 421 



for all other individuals not closely related to the individual whose corpuscles 

 were employed for the exhaustion of the serum. 



(N.B. — It is possible that exceptions may be found, but these have not yet 

 been met with except in the case of close blood-relations.) 



8. The red blood corpuscles of any individual are thus characterised by a 

 definite individuality of their own, and can be distinguished from those of any 

 other individual of the same species. 



Experimeyital Researches on Vegetable Assimilation and Respira- 

 tion. VI. — Some Experiments on Assimilation in the Open Air. 



By D. Thoday, M.A., Junior University Demonstrator in Botany, 



Cambridge. 



(Communicated by Dr. F. F. Blackman, F.E.S. Received March 1, — 

 Eead June 16, 1910.) 



CONTENTS. 



PAGE 



Section I. — Introduction 421 



IL — On the Eate of Assimilation of Carbon Dioxide by Leaves 



of Helianthus mmuus in Bright Sunshine 422 



i. Experiments , 422 



ii. Discussion of Results 430 



iii. Brown and Escomb'es Experiments with H. annuus... 433 



III. — Experiments with Catalpa hignonioides 435 



IV. — On the Rate of Assimilation in Nature, and on the Occur- 



rence of Translocation during the day 439 



v.— Summary 447 



Section I. — Introduction. 



In investigating assimilation under natural conditions, gasometric methods, 

 w^hich involve enclosing leaves, are unsuitable. The only method which is 

 free from this objection is the half-leaf dry-weight method introduced by 

 Sachs.* Unfortunately, owing to the overlooking of certain grave errors to 

 which this method is liable, most of the earlier work is of uncertain value. 

 Having, however, made a full investigation into the sources and magnitude of 

 these errors, an account of which was published in an earlier paper,t I have 



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

 t 'Roy. Soc. Proc.,' 1909, B, vol, 82, p. 1. 

 VOL. LXXXII. — B. 2 L 



