NUTRITION 63 



or foi mic aldehyde with the already complex molecules of the 

 pigments. By the same living agent, with or without solar 

 energy, these molecules may be split into chlorophyll and 

 sugar, but the chlorophyll pigments are so many that no 

 one reaction or series of reactions will truthfully represent 

 the process in all plants. The problem remains unsolved, 

 and suggestive as the deductions of chemists are, its solu- 

 tion is to be expected from physiologists equipped with 

 chemical knowledge rather than from chemists devoid of 

 physiological experience. 



In summing up this part of our study of the nutrition of 

 plants, we may say that the non-nitrogenous foods, which 

 first appear in the cells as sugars ( cane and grape ) , mannit, 

 etc., starch, fats, and oils, are formed from carbon-dioxide 

 and water in the chromatophores (starch) or in the next 

 adjacent cytoplasm (oil) by these living organs of the cell, 

 the energy necessary for this synthetic process being ab- 

 sorbed by the lifeless chlorophyll pigments and used by the 

 living protoplasm. 



These non-nitrogenous foods accumulate temporarily in 

 the plastids ( starch ) , the cytoplasm ( oil ) , and the cell-sap 

 (sugars). The manufacture of these foods can be accom- 

 plished only during the hours when the plant can secure the 

 necessary energy, i. e. while it is suitably illuminated. The 

 removal of the manufactured product goes on independently 

 of the illumination, for whenever the food is in soluble form 

 and in solution, it will diffuse out of the cells in which it is 

 made into others containing smaller amounts of these sub- 

 stances. This diffusion goes on constantly, the rate of 

 diffusion varying only with the differences in the amounts of 

 the foods in the different cells. While the plant is strongly 

 illuminated, however, the rate of manufacture is higher than 

 the rate of removal by diffusion, and the food accumulates 

 at this time in the cells forming it. Hence, in the early 

 morning, we may find the chlorophyll-containing cells free 

 from starch, oil, and anything more than small amounts of 

 sugar, at the close of the day, full of them. If, because of 

 prolonged or too intense illumination or because of any 

 other unusual circumstance, the rate of manufacture exceeds 



