THE CHLOROPHYLL APPARATUS 155 
formaldehyde. The new acid, H,CO,, 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- 
