390 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the same way in from eight to ten clays, as well as in many other 

 cases. The author believes, therefore, that the first demonstrable 

 product of the decomposition of carbon dioxide is not starch, but 

 sugar, and in all probability this is really the first product formed. 



Distribution of Energy in the Chlorophyll-spectrum.* — C. Timi- 

 riazeif points out the intimate relationshiii between the absorption of 

 light by cliloroj)hyll and the intensity of the chemical phenomena 

 produced, the curves of absorption of light and of the decomposition 

 of carbon dioxide presenting an almost exact concurrence. This 

 last function may be considered as dependent on the energy of radia- 

 tion as measured by its effect on the thermopile. Langley has 

 definitely fixed the position of maximum energy in the solar spectrum 

 to be in the orange, exactly in that part which corresponds to the 

 characteristic band of chlorophyll, between B and C 



It results, therefore, that chlorophyll may be regarded as an 

 absorbent specially adapted for the absorption of those solar rays 

 which have the greatest energy ; and its elaboration by the vegetable 

 economy is one of the most striking examjiles of the adaptation of 

 organized beings to the conditions of their environment. 



Under the most favourable conditions 40 per cent, of the solar 

 energy corresponding to the rays of light absorbed by the charac- 

 teristic band of chlorophyll, is transformed into chemical work- 

 Chlorophyll therefore constitutes an apj)aratus of great perfection, 

 capable of transforming into useful work 40 per cent, of the solar 

 energy absorbed. 



Colour and Assimilation.l — T. W. Engelmann has made an 

 extensive use of the so-called bacteria method for investigating the 

 effect of light on chlorophyll-cells, and he now gives further details 

 of his experiments, with some of his conclusions. 



The effect of free oxygen upon quiescent bacteria is so gi-eat that 

 by their presence the trillionth of a milligram of the gas can be 

 detected. When a green cell in water is evolving oxygen, even to an 

 extremely minute amount, the movements of the bacteria afford 

 instantaneous indication of its presence. Moreover, when the ray of 

 light, shining through or on the green cell, is unfavourable to the 

 process of assimilation and evolution of oxygen, the effect on the 

 bacteria is at once shown. All of Engelmanu's experiments were 

 checked by control observations. The results are mainly as follows : — 

 Only those cells which contain particles of coloured jirotoplasm evolve 

 oxygen in the light. When colourless protoi)lasm was screened by a 

 coloured solution, or was illuminated by light coming through a green 

 leaf, no oxygen was evolved. It will be seen that this has a direct 

 bearing upon some of Pringsheim's views. In the case of cells of 

 different colours, e. g. green. Sphagnum and Spirogyra ; yellowish- 

 brown, Navicula and Pinnularia; bluish-green, Oscillatoria and Nostoc; 

 red, Callithamnion and Ceramium; distinct relations between the colour 

 and the amoimt of assimilation under different rays were made out. 



• Comptos Ecnclus, xcvi. (1883) pp. 375-6. 

 t Bot. Ztg., xli. (1883) pp. 1-13, 17-29. 



