456 METABOLISM IN LIVING PLANTS. 



up and consumed by the plant. In this way, without doubt, a reduction of 

 the carbon of the carbon dioxide occurs, and hand in liand with this reduction 

 a union of carbon with water must take place. Thus is formed some one 

 of the compounds known as carbohydrates. The process has been interpreted 

 in the following manner. The carbonic acid is reduced in the green cells, by 

 the separation of oxygen, to carbon monoxide; this combines with hydrogen to 

 form a body known by the name of formic aldehyde, and from this is produced, 

 by the action of alkaline substances, a carbohydrate. This latter process is 

 more easily understood, from the fact that it has been found possible to produce 

 a sugar from the formic aldehyde (which consists of one atom of carbon, one 

 of oxygen, and two of hydrogen) by means of lime. Thus a definite carbohydrate 

 would be established as the first organic substance formed in a vegetable cell. 

 It is scarcely probable, however, that this carbohydrate alone forms the starting- 

 point for the whole of the other organic compounds in all living plants. It is 

 much more likely that in the large, fundamentally difierent series of plant-forms, 

 in Fucacese, Florideae, mosses, ferns, conifers, grasses, palms, &c. different carbo- 

 hydrates are produced as the first organic derivatives of carbon dioxide and water. 

 It must not be forgotten that in this building process the protoplasm of the 

 green tissue plays a very important part, that this is actually the builder, and 

 that the structure and chemical composition of the constructor, or, in other 

 words, the specific constitution of the protoplasm, will not be without influence 

 on the arrangement of the atoms in the carbohydrate formed. The whole of 

 this process has been termed assimilation, and by it is meant that the protoplasm 

 in each plant forms materials from the inorganic food absorbed, resembling those 

 of which the protoplasm itself is made up. Assimilating protoplasm thus con- 

 tinues to organize after its own type, and in this matter cannot pass beyond 

 the bounds drawn for it by its own atomic construction. The assumption is 

 now justified that in these formative processes assimilation takes efiect from the 

 beginning, and that protoplasm which exhibits a difierent constitution, and which 

 is known to have the capacity of choosing between the mineral food-salts, will 

 form different carbohydrates. However this may be, this much is certain, that 

 the first organic compound arising in the green cells is a kind of sugar or some 

 other dissolved, undemonstrable carbohydrate. 



Under the influence, and by the means of living protoplasm, and in accordance 

 with the requirements of the plant species in question, very diverse alterations 

 and the most varied arrangements and connections, insertions and separations 

 of the atoms are carried on in these primary carbohydrates, and as long as the 

 plant is alive, a continuous transformation of the materials takes place. And 

 this transformation is carried on in very many directions. First, compounds 

 are formed indirectly or directly from the primary carbohydrates. They con- 

 tribute to the extension of the protoplasm and the envelopes produced from it. 

 Without them no increase in cells, or growth of the plant, would be possible. 

 They may be fitly termed the building materials. 



