THE CHLOROPHYLL APPARATUS 155 



formaldehyde. The new acid, H 2 C0 4 , splits up into carbon 

 dioxide and hydrogen peroxide, and the latter is decomposed 

 into water and free oxygen. 



All these views must be regarded rather as ingenious 

 speculations than as sound hypotheses resting upon observa- 

 tion and experiment. 



A theory of a totally different nature was advanced 

 some years ago by Vines. Starting with the observation 

 that a carbohydrate substance (cellulose) is produced or 

 secreted by protoplasm in the process of the thickening of 

 cell-walls, and noticing the formation of starch grains in 

 the chloroplast almost as soon as the photosynthesis 

 has been established, he argues that the carbohydrate is 

 not directly formed from the simple materials absorbed, 

 but appears as a secretion product of the chloroplast. 

 He suggests that a body possibly allied to formaldehyde 

 is first formed according to Baeyer's theory, and that this 

 is used in the construction of protein, by combining with 

 the nitrogen and sulphur absorbed in the form of salts 

 from the soil, or with nitrogenous substances derived from 

 previous decompositions of protein. This protein then is 

 assimilated by the protoplasm of the chloroplast, and from 

 the latter the carbohydrate (starch) is secreted. 



This view, while no doubt, in the main, accurate as far 

 as the mode of formation of starch is concerned, cannot be 

 regarded as explaining the formation of carbohydrates from 

 the simple compounds absorbed. The leucoplast of the 

 tuber, as well as the chloroplast itself under certain con- 

 ditions, can form starch grains when supplied with sugar 

 in the absence of carbon dioxide, and in all probability the 

 appearance of the starch is the result of the presence of an 

 excess of sugar in the leaf -cells. Regarded as an explanation 

 of the photosynthesis of carbohydrates, it, like the others, 

 must remain hypothetical. Moreover it is based upon the 

 assumption that starch is the highest term reached in the 

 plant in the series of carbohydrate bodies. This assump- 

 tion, however, is not supported by the evidence at our com- 



