322 PHYSIOLOGY OF NUTRITION. 



129. Quantitative Chemical Researches on the Behaviour of 

 Fats and Carbohydrates in Plant Metabolism.* 



The study of the processes exhibited in the germination of seeds 

 is very well adapted to explain the behaviour of fats and carbo- 

 hydrates in metabolism. We first endeavour to determine the 

 percentage composition of the seeds, and of the products of their 

 germination which have been obtained in the manner given in 

 128, and then, in order to obtain comparable numbers, reduce the 

 results to 100 gr. of seed dry- substance, and the quantity of 

 seedling dry-substance obtained from 100 gr. of seed dry-sub- 

 stance. If, e.g., 100 gr. of seed substance has yielded 90 gr. of 

 seedling substance, the values for the percentage composition of 

 the seedlings must be reduced to a total of 90 gr. The analysis 

 of the seeds and seedlings is made as follows : 



About 3 gr. of the dry substance (seed or seedling) very finely 

 powdered, is extracted with ether in the manner indicated in 120 

 for determination of the fat. The residue from the fat determina- 

 tion is repeatedly digested for some time with water at the 

 ordinary room temperature. After filtering, the fluid is made up 

 to 200 c.c. Of this, 50 c.c. are used for the determination of 

 sugar (see 115), and 50 c.c. more, after the fluid has been boiled 

 with a little Sulphuric acid, for the determination of dextrin 

 (see 116). 



We treat the residue extracted with water, or better about 3 gr. 

 of fresh seed or seedling material (in very fatty seeds or seedlings 

 the fat must first be removed), in a flask of about 500 c.c. 

 capacity, with 200 c.c. of water, boil for some time till the starch 

 has quite thickened, and digest the fluid for about two hours 

 longer at a temperature of 70 C. after adding a few drops of 

 Hydrochloric acid. We then allow to cool, make up to 500 c.c., 

 let settle, and filter off 200 c.c. through a dry filter. We mix the 

 clear filtrate with 15 c.c. of 25 per cent. Hydrochloric acid, boil 

 for three hours, replacing the water lost by evaporation, and after 

 allowing to cool again make up to 200 c.c. In 50 c.c. of the fluid 



* Many valuable methods have lately been discovered for accurately deter- 

 mining the quantity of the different bodies present in seeds and seedlings. 

 This is not the place to go into such details. We must hence consult the 

 recent literature on agricultural chemistry and Konig's book already frequently 

 cited. 



