METABOLIC PROCESSES IN THE PLANT. 303 



E. v. Wolff's l method. The carefully cleaned roots are cat into 

 slices, and 500-1000 gr. of these slices are hung up by threads in 

 the drying chamber at a temperature of 60-70C. The dry mass 

 is pounded to a not too fine powder and weighed, and then the 

 amount of dry substance in a small quantity of it (5-6 gr.) is 

 determined. A quantity of the powder (2-3 gr.) is repeatedly 

 boiled with 80-85 per cent, alcohol, the solution being filtered 

 after each boiling, and finally the residue on the filter is washed 

 with hot alcohol. To the whole solution we now add a large 

 quantity of water, and warm on the water- bath till the alcohol has 

 completely evaporated. The fluid is now made up to 300 c.c. 

 In 100 c.c. of it we at once determine the grape-sugar with 

 Fehling's solution ; it must, however, be remembered that the 

 grape-sugar is very small in quantity, if not entirely absent. To 

 200 c.c. of the fluid we add four drops of Sulphuric acid, and warm 

 on the water-bath for three hours, adding water to replace that 

 lost in the process. We then make up to 400 c.c., and after 

 neutralising with Sodium carbonate determine the amount of 

 grape-sugar present in 100 c.c. by means of Fehling's solution. 

 From the numbers obtained it is easy, finally, to calculate the 

 amount of cane-sugar in fresh roots, or in dry root substance. As 

 regards the preparation and method of using Fehling's solution, 

 all that is requisite has been already given (see 111). 



From what has been said, it is at once clear how we must pro- 

 ceed to detect qualitatively the presence of cane-sugar in roots. 



To detect cane-sugar in roots microchemically, the sections, 

 which must not be too thin, so that all the cells are not opened, 

 are treated as described in 115 with Copper solution and potash. 

 On examining the sections under the microscope, it is found that 

 the contents of their cells has taken on a beautiful blue colour 

 which indicates the presence of cane-sugar. 2 The reaction takes 

 place when the sections are mounted in a drop of Fehling's solu- 

 tion, covered with a cover-glass, and warmed (see 115). 



1 See E. von Wolff, Anleitung zur chem. Unters. landwirthschl. wichtiger 

 Stoffc, 1875, p. 184. 



2 See Sachs, Pringsheim's Jahrbiicher, Bd. 3, p. 183. 



118. Reserve Cellulose and Amyloid. 



In the seeds of many plants cellulose is present as\ nitrogenous 

 reserve substance. A date stone is halved transversely, and then 



