METAHOLir. PJKM 'ESSES IN THE PLANT. 323 



we determine the sugar by means of Fehling's solution, and then 

 calculate the corresponding quantity of starch (see 111). 1 



The residue left after treating with Hydrochloric acid, we boil 

 for half an hour with 200 c.c. of 1 per cent, potash solution, filter, 

 and boil the mass remaining on the filter for half an hour with 200 

 c.c. of water. The residue still left is collected on a weighed filter 

 paper, washed with alcohol and ether, dried and weighed. From 

 the quantity of raw fibre obtained must be deducted the weight of 

 ash and the quantity of proteid present in it, both of which must 

 be determined. 



Special portions of the seed and seedling material are taken for 

 the determination of the ash. The quantity of proteid present in 

 the seeds and seedlings must likewise be determined, and possibly 

 also the quantity of asparagin, etc. (see 99). 



In calculating the percentage composition of seeds and seed- 

 lings from the results of the experiments we have made, there 

 always remains a not inconsiderable deficiency. The quantity of 

 " undetermined substances " must, however, be specified. 



As to the significance of quantitative chemical experiments in 

 the study of metabolism, I have spoken fully elsewhere. 2 It need 

 only be mentioned here that by this method we can, e.g., clearly 

 make out in what relation the amount of starch vanishing in 

 metabolism stands to the amount of dry substance disappearing, 

 how much sugar is produced under particular conditions, how 

 much starch is formed in the germination of fatty seeds when a 

 certain amount of fat has disappeared, and so forth. All these 

 questions are of high scientific interest/' 



1 See also Konig, Untersuchung landwirtlischl. ivichtigcr Ktoffe, 1891, p. 231. 



2 See Detmer, Vergldchemle Physiologic d. Keimungsprocesses der Samcn, 

 1890. 



3 See also in the places indicated the literature. Also see Detmer, Physiol. 

 Untersuchungen Hber die Keimung olhaltiger Samen und die Vegetation von Zea 

 Mays, 1875 ; Detmer, in Wollny's Forschnngcn auf dem (lebiete der Agricultur- 

 l>hysik, Bd. 2. And Saclisse, Ueber einige chcm. Vorgange bei der Keimung con 

 Pisum sativum, 1872. 



