142 



Carbon Assimilation. 



Troposolum iiiajus, September 11th, 1900 



Leaves in sunlight under canvas screen. 



Duration of experiment 4*8 hours. 



Assimilation of COj per sq. decimetre per hour , 

 Transpiration of water „ „ ,, 



1-210 c.c. 

 01340gm. 

 0-1282 gm.-cal. 

 0-700 



00897 gm.-cal. 

 0-0010 „ „ 

 0-0132 „ „ 

 0-0142 „ „ 

 0-0755 „ „ 



Solar radiation incident on leaf per sq. cm. per mi 

 Coefficient of absorption „ „ 



Solar radiation absorbed by the leaf ,, „ 

 Energy expended in assimilation „ ,, 

 ,, ,, „ transpiration ,, „ 



Total Energy used for internal work „ „ 

 Enerjjy lost by re-radiation and convection ,, 



In the following table we give the summary of the energy 

 relations as estimated by Brown and Escombe in five such experi- 

 ments on Polygonum Weyrichii. 



Table XLllI. 



Mode of Disposal of Energy by the Leaf of Polygonum Weyrichii. 



Total Energy Received 100. 



In order to indicate the conditions of experiment, we give overleaf 

 (Table XLIV) the actual experimental data of these five experiments 

 as recorded by Brown and Escombe. 



We do not intend to analyse in detail the results obtained by 

 Brown and Escombe, as for reasons already given, we consider that 

 at present it is not possible to obtain absolute values of the energy 

 used in different processes; More light must be shed on the 

 complexity and influence of the various factors before such 

 numbers as Brown and Escombe's can be discussed with profit. 



How much importance can be attached to such calculated 

 values is indicated by the estimations of leaf temperature by Brown 

 and Escombe. To obtain this they start with the assumption that 



