THE TRANSLOCATION OF CARBO- 

 HYDRATES IN PLANTS 



PART II 



By S. MANGHAM, B.A. 



Late Exhibitioner, Emmanuel College, Cambridge , and University Frank Smart 

 Student in Botany 



In the first part of this article * an attempt was made to show 

 that a detailed examination of the structure and relations of 

 plant tissues, in particular those of the leaf, makes it appear 

 highly probable that the whole of the products of photosynthesis 

 are translocated in the sieve-tubes, in accordance with the 

 theory put forward by Czapek in 1897. It is now necessary to 

 see how far the theory suggested by a study of structure is 

 supported by the results of physiological experiments. 



The experimental investigations of the problem may be 

 divided into two classes. In the one the paths of translocation 

 of food materials were sought by observing the results of inter- 

 rupting possible paths by removing a portion of the tissues. 

 Such surgical operations, whilst yielding instructive results, 

 scarcely enable sound conclusions to be drawn as to the role 

 of individual cells, as from the nature of the case it is practically 

 impossible to interrupt the paths that may be formed by some 

 types of cells {e.g. sieve-tubes) without affecting others near 

 them. Consequently the inferences drawn apply for the most 

 part to whole tissues only and to a much less degree to their 

 constituent elements. 



More exact knowledge has been afforded by the other class 

 of experiments in which the contents of individual cells have 

 been examined by chemical and microchemical methods. In 

 this way the amount and distribution of various substances in 

 the plant have been made out with a fair degree of accuracy ; 

 by varying the experimental conditions it has been possible to 

 follow the path of the sugars much more closely. 



* Part I. appeared in Science Progress, October 1910, pp. 256-85. 



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