METABOLIC PROCESSES IN THE PLANT. 



305 



quantities of the inuliii into glucose. If we boil an aqueous 

 solution of inulin after addition of a few drops of Sulphuric acid, 

 a considerable quantity of glucose is produced, and the fluid 

 no\v reduces Fehling's solution very energetically. 



It is noteworthy that if a hot solution of inulin be allowed to 

 cool, the inulin does not at once 

 separate out, but only after some 

 time. If, however, to a solution 

 of inulin which has just cooled 

 we add a large excess of alcohol, 

 the separation of the inulin quickly 

 follows. The insolubility of inulin 

 in alcohol is utilised in testing for 

 the substance microcliemically. 

 Sections, not too thin, are cut 

 from the pith of tubers of Dahlia 

 variabilis, covered with alcohol, 

 and after some time dipped in 

 water. On examining the sections 

 under the microscope in water, the 

 inulin is seen to have separated 

 out. Under some circumstances 

 the inulin separates out in the 

 cells in the form of sphere 

 crystals. These are very clearly 

 seen, if we allow fairly large 

 pieces of Dahlia tubers to remain 

 in spirit for at least eight to 

 fourteen days, and then prepare sections from the alcohol material,, 

 and examine them in water. The sphere crystals are seated on 

 the cell- walls as globular structures of characteristic appearance 1 

 (see Fig. 110). 



FJG. 110. Cell from a piece of a tuber 

 of Dahlia variabilis, which had been 

 kept for several months in alcohol. 

 Sphaero-crystals on the walls. Magn. 

 240. (After Strasburger.) 



1 See Sachs, liotanixche Zcituny, 1864, p. 25, and Prantl, Das Inulin > 

 Miinchen, 1870, 



120. Vegetable Fats and their Quantitative Determination. 



If we extract dried and pounded plant material with ether, we 

 obtain a solution which, 011 evaporation, yields a residue consisting 

 essentially of fat. Usually the quantity of other substances mixed 



P.P. 



