ORGANIC SUBSTANCES AS PLANT FOOD 217 



siderably increased in an acid medium (pH5), and since in saponifi- 

 cation free acids accumulate, the activity of lipase has an auto- 

 catalytic character. In the beginning it proceeds rather slowly, 

 and then with ever-increasing rapidity. 



The transformation of fats in germinating seeds is not limited 

 to their hydrolysis and the accumulation of fatty acids. The latter 

 very quickly undergo further changes, and in their place sugars 

 appear in considerable quantity. Thus, in one of Frankfurt's 

 experiments the seeds of sunflower contained 55.3 per cent of fats, 

 3.8 per cent of sugars, while in the sprouts, there had remained 

 21.8 per cent of fat, but the sugars had increased to 13.1 per cent. 

 In the more advanced stages of germination the surplus sugar may 

 even be transformed into starch. 



The process of the transformation of fatty acids into sugars in 

 the germination of seeds generally proceeds very easily in plants 

 just as does the reverse process in maturing seeds — the formation 

 of fat from carbohydrates. It has not been possible as yet, however, 

 to produce this transformation artificially, its chemical nature 

 remaining unsolved. Basically, this transformation of fats into 

 sugars is an oxidation process and is accompanied by the absorption 

 of oxygen, while in ripening seeds a reduction process takes place. 

 The intermediate products of these processes apparently are alde- 

 hydes and oxyacids. 



A group of substances closely related to the fats are the lipoids, 

 or fatlike substances. The most important representative of this 

 group is lecithin, a complex ester composed of glycerine, two fatty 

 acids, and phosphoric acid, which in its turn is united with a strong, 

 nitrogen-containing, organic base. The general formula of leci- 

 thin is: 



^(CH 3 )3, 

 CH 2 (OOCR) CH(OOCR) • CH 2 • PO(OH) • O • C 2 H 4 • N\ 



x OH 



in which RCOO represent the remains of various fatty acids. In 

 hydrolysis, lecithin splits into fatty acids, choline, 



(CH 3 )3<&. 



^N-C 2 H 4 OH, 



oh/ 



and glycero-phosphoric acid, CH 2 OHCHOHCH 2 OPO(OH) 2 . 

 The various lecithins differ from each other in respect to the 



