198 ORIGIN OF ORGANIC MATTER 



day is suffered to remain in the atmosphere surrounding the plant, 

 and is not removed by the agency of chemical means. 



It still remains for us to notice a hypothesis advanced by 

 Mulder in explanation of the process of deoxidation in plants, as 

 it leads us to the consideration of a point to which we have 

 scarcely made a distant allusion in the above-mentioned hypo- 

 theses. As the property of absorbing carbonic acid and of exhaling 

 oxygen is limited to the green parts of a plant, the idea naturally 

 presents itself that the chlorophyll on which this colour depends 

 plays a very important part in this process of reduction ; although 

 we are unable to decide, from the facts before us, whether the 

 chlorophyll acts in the manner of a ferment, or whether this 

 interchange of gases is dependent upon the formation of the 

 chlorophyll from bodies richer in oxygen. Mulder has advanced 

 the following hypothesis, which presents considerable plausibility. 

 According to his view, new chlorophyll is always being formed 

 under the influence of light, whilst the more richly oxygenous starch 

 is simultaneously converted into wax, which is poorer in oxygen, 

 wax being, as is well known, constantly present, together with the 

 chlorophyll. On the other hand, microscopical observations of 

 the development of cells and their contents render it very probable 

 that granules of starch are gradually converted into globules of 

 chlorophyll, which are rich in wax. Mulder supposes that the 

 oxygen which is developed during the formation of wax from 

 starch goes partly to the colourless chlorophyll, to convert it into 

 the green variety, and that is partly given off, in a free state, to 

 the surrounding atmosphere. Draper is more disposed to regard 

 chlorophyll as a ferment, and he urges, as a proof of the decom- 

 position of the (nitrogenous) chlorophyll, the above-mentioned 

 fact that plants always develope some nitrogen in addition to the 

 oxygen which they give off in solar light. 



The nitrogenous compounds generally, and more especially 

 those which are included under the term protein-bodies, play no 

 less important a part in the life of plants than in that of animals ; 

 and there is no living cell in the plant which does not contain 

 albuminous substances, either in the primordial utricle, or in some 

 other form. Wherever the vital activity of the plant is most 

 powerfully developed, the cells are found to be most richly 

 endowed with these substances ; as, for instance, in the fibrils of 

 the roots, as well as in the flower and leaf-buds, in the pollen 

 granules, in the embryonic sac, and more especially in the seeds. 

 Although these local relations sufficiently indicate the importance 



