Studies of photo-synthesis in fresh-water algœ. —1. The fixation of both carbon and nitrogen from the atmosphere to form organic tissue by the green plant cell. 2. Nutrition and growth produced by high gaseous dilutions of simple organic compounds, such as formaldehyde and methylic alcohol. 3. Nutrition and growth by means of high dilutions of carbon dioxide and oxides of nitrogen without access to atmosphere

Abstract

The two most primæval and most fundamental chemical processes for living organisms are those two in which their living substance is synthesised from inorganic sources with uptake of energy. By one of these carbon is built into organic compounds, starting with the oxidised carbon dioxide of the atmosphere and utilising the energy of sunlight. The source of the inorganic nitrogen, which in the second is likewise built into organic forms in the amino-acids and proteins, is more obscure, and has in the course of 150 years led to much disputation. In the present and succeeding papers evidence will be adduced that the source of the nitrogen utilised by the plant does not lie in the soil (although a luxury or luxus supply may be given from the soil), but in the air, and that the reaction by which the atmospheric nitrogen and oxygen are made reactive is a photo-synthetic one, in which the energy of sunlight is absorbed and converted into chemical form as nitrites in the green cell. This view places these two processes of carbon and nitrogen assimilation upon the same basis, and make them coeval in the process of evolution; this, as will presently be pointed out, must have been the case, in order that any living organism could ever have appeared upon the earth.