44 Literature on Inosite-Phosphoric Acid [Sept. 



those which had snnlight. Opaque shields on the leaves produced 

 the same results in the protected part of the leaf, hence the change 

 of inorganic into organic phosphorus may be attributed in part if not 

 altogether to photosynthesis. Stoklasa and his pupils^'* consider 

 phosphorus an integral part of Chlorophyll, existing in a form which 

 does not give the HPO4 ion. Schimper^^ in his rather comprehen- 

 sive study of the assimilation of the ash constituents in plants also 

 noted the decrease of the inorganic phosphorus through the action 

 of light. Posternak, attempting to account for the formation of 

 "phytin," which he then thought to be anhydro-oxymethylene-di- 

 phosphoric acid, assumed that it was formed simultaneously with 

 the reduction of carbon dioxide by a direct combination of the orod- 

 ucts of the photo-chemical action and inorganic phosphates, an 

 hypothesis suggested by Schimper's experiments. If Posternak's 

 assumption is true, even in part, phosphorus may play a very signi- 

 ficant röle in carbohydrate anabolism. Several authors have ex- 

 pressed doubt about this explanation of "phytin" synthesis, advanc- 

 ing the argument that inosite-phosphoric acid is not found in the 

 early stages of growth, and when formed later is not uniformly 

 produced, as would be expected if it were due entirely to the action 

 of the chloroplasts. There is still the possibility that it is so syn- 

 thesized and instantly broken down in the formation of other Com- 

 pounds. 



Soave could find no inosite in dormant seeds unless they were 

 first boiled in strong acid, but after they began to sprout its pres- 

 ence could be easily demonstrated until the reserve material of the 

 cotyledons was almost exhausted. It was also present in unripe 

 seeds, indicating that the inosite-phosphoric acid is formed in the 

 seed by the combination of the inorganic phosphorus, abundantly 

 present at this stage, with the inosite. The occurrence of inosite in 

 the unripe seed and the green parts of the mature plant, and the later 

 disappearance of this substance as inosite-phosphoric-acid -forms, 

 indicate that phytin is probably produced by the reversible action 

 of an intracellular phytase, and that Posternak's explanation is in- 

 correct. 



Rising suggests that inosite-phosphoric acid may be an interme- 



** Stoklasa, Brdlika and Ernest : Ber. d. deut. bot. Ges., 1910, 27, i, 

 "Schimper: Flora, 1890, 23, 207-261; Bot. Zeifg., 1888, 46, 81. 



