570 Presence of Inorganic Iron Compounds in Chloroplasts. 



dicotyledonous plants were examined and it was found that here the 

 transition from dark brown to blue-black was much slower as a rule, and 

 in some cases the staining remained permanently of a deep orange-brown 

 to a pure dark brown colour. But in all cases the chloroplasts stained 

 more deeply than the remainder of the cytoplasm. 



The catalyst for the photo-synthesis may not in all cases be an iron salt, 

 or oxide, but an iron salt is present and capable of operating as a catalyst 

 in a large number of instances. 



Various substances known to be present in the ash of leaves have been 

 tested for their photo-synthetic activity in connection with the work, and it 

 has been found that magnesium and calcium phosphates and bicarbonates are 

 entirely ineffectual, but that marked photo-synthesis of formaldehyde is 

 obtained with chlorides or colloidal hydrates of iron or aluminium. 



Summary. 



1. Inorganic iron salts and iron or aluminium hydrates in colloidal solution 

 possess the power of transforming the energy of the sunlight into chemical 

 energy of organic compounds. 



2. Inorganic iron, in crystalloidal or colloidal form, is present in the 

 colourless part of the chloroplast of the green plant cell in many plants. 



3. In the absence of iron the green colouring matter cannot develop in 

 the leaf, although the green colouring matter itself contains no iron. 



4. In the presence of sunshine, the iron-containing substance of the 

 chloroplast develops the colouring matter, so that this itself is a product 

 of photo-synthesis induced by the iron-containing compound. 



5. These facts afford an explanation of chlorosis, and its cure by inorganic 

 iron salts, and demonstrate that iron is a primary esseutial in photo-synthesis, 

 and the production of chlorophyll. 



6. The iron-containing substances of the colourless portion of the chloro- 

 plast, and the chlorophyll produced by them, then become associated in the 

 functions of photo-synthesis as a complete mechanism for the energy trans- 

 formation, 



My thanks are due to my colleague, Prof. E. J. Harvey Gibson, for much 

 valuable advice in selecting and obtaining suitable material, and to Misses 

 E. M. Blackwell, M. Knight, and B. Bobbins, of the Botanical Department of 

 the University of Liverpool, for supplies of fresh material. 



