EVOLUTION OF ALG^E loi 



be, and how much has yet to be accompHshed before we can 

 picture to our minds with any degree of certainty the changes 

 that take place when Hght is absorbed by it. But the evidence 

 afforded by the action of hght upon other organic compounds, 

 especially those which, like chlorophyll, are fluorescent, and 

 the conclusion according to modern physics teaching that we 

 may regard it as practically certain that the first stage in any 

 photochemical reaction consists in the separation, either par- 

 tial or complete, of negative electrons under the influence of 

 light, leads us to conjecture that, when absorbed by chloro- 

 phyll, the energy of the light-waves becomes transformed into 

 the energy of electrified particles, and that this initiates a whole 

 train of chemical reactions resulting in the building up of the 

 complex organic molecules which are the ultimate products of 

 the plant's activity." 



Chlorophyll absorbs most vigorously the rays between B 

 and C of the solar spectrum,^ which are the most energizing; 

 the efl'ect of the rays between D and E is minimal; while the 

 rays beyond F again become effective. As compared with the 

 primitive bacteria in which nitrogen figures so largely, chloro- 

 phyllic plant tissues consist chiefly of carbon, hydrogen, and 

 oxygen, the chief substance being cellulose (CeHioOo),- while in 

 some cases small amounts of nitrogen are found, and also min- 

 eral substances — potassium, magnesium, phosphorus, sulphur, 

 and manganese. Chlorophyllic algal life is thus in contrast 

 with bacterial life, the prime function of which is to capture 

 nitrogen. 



Evolution of the Alg.^ 



Closest to the bacteria in their visible structure are the so- 

 called "blue-green algae" or Cyanophyceoe, found almost every- 



' Loeb, Jacques, 1906, p. 115. 



^ Pirsson, Louis V., and Schuchert, Charles, 1915, p. 164. 



