12 



In order to observe how a deficiency of phosphoric acid would inter- 

 fere with the normal action of plant cells the writer compared at a low 

 temperature the behavior of alga? {Spirogyra) in complete culture solu- 

 tions ^ with that of alg* cultivated for eight weeks in solutions free from 

 phosphoric acid, but containing all other necessary mineral nutrients. 

 The result was that there was no growth in the absence of the phos- 

 phoric acid, but there was a yellow coloration of the chlorophyll and 

 an accumulation of fat and albumin, while in the control algse the 

 number of cells had more than doubled, the coloration of the chlorophyll 

 was normal, and the amount of fat and albumin stored up was much 

 smaller than in the former case. When, however, at the end of eight 

 weeks, 0.1 per mille of monopotassium phosphate was added to the 

 culture free from phosphoric acid, a most energetic cell division began 

 in most of the cells after a short time, thus demonstrating the great 

 importance of phosphoric acid for this purpose. 



A direct participation of inorganic phosphates in the formation of 

 albumin, as Liebig had assumed, has not been proved, and is improb- 

 able. As the writer has observed, cells of algae can continue to form 

 albumin for a certain length of time, even in the absence of inorganic 

 phosphates, although further growth and multiplication will thus be 

 stopped.'^ 



THE PHYSIOLOGICAL IMPORTANCE OF LECITHIN. 



This ester of phosphoric acid contains fatty acids, glycerol, phos- 

 l)horic acid, and choline, and corresponds to the following formula:^ 



CH2-0-(/) 





H2— O — (/) Qg 



H2— o— p=o 



It is a regular concomitant of fatty matter. It swells up in water and 

 is even somewhat soluble in it, a property which renders it physiolog- 

 ically superior to the ordinary fatty matter. The chief function of 

 lecithin is probably to serve for respiration; it represents the form into 



' The composition of the solution made with distilled water was as follows for the 



control culture : 



Per mille. 



Potassium nitrati; 0.2 



Calcium nitrate 0. 2 



Sodium sulphate 0. 1 



Magnesium sulphate 0. 1 



Monopotassium phosphate 0.1 



ferrous sulphate Trace. 



The monopotassium phosphate was left out in one of the solutions. 



2 Biol. Centralbl., 1891, Vol. IX, No. 9. 



3(/) Signifies the radical of a higher fatty acid; (cA) signifies the radical of 

 choline. 



