304 PHYSIOLOGY OF NUTRITION. 



a delicate transverse section of the endosperm is prepared from it 

 by means of a very sharp razor. The walls of the elongated cells 

 are exceedingly thick, but numerous simple pits are present. We 

 treat a section with iodised Potassium iodide solution, and then 

 run in from the margin of the cover-glass dilute Sulphuric acid, 

 prepared by mixing 2 parts by volume of Sulphuric acid with 

 1 part by volume of water. The thickening layers of the cell- 

 wall stain beautifully blue. If sections of the endosperm are 

 treated in the manner previously described (see 42) with phloro- 

 glucin solution, and then with Hydrochloric acid, the walls do 

 not take on a red coloration. The thickening layers of the cell- 

 walls of the endosperm cells are therefore not lignified; they 

 consist of cellulose. In the germination of the date seed this 

 cellulose is made use of. 



The material is not, however, absolutely identical with ordinary 

 cellulose, as recent investigations, e.g. those of Reiss (Land- 

 wirfhschaftl. Jakrb., 1889) have shown, and it is hence distinguished 

 as "reserve cellulose." 



In the cells of the cotyledons of dormant seeds of Tropreolum 

 majus are present, as is easily seen in examination of transverse 

 sections, parenchymatous elements which are provided with 

 strongly thickened pitted membranes. Between the cells are 

 three-cornered intercellular spaces. The thickening layers stain 

 blue on direct treatment with dilute iodised Potassium iodide 

 solution; they consist not of reserve cellulose but of amyloid. 

 This amyloid is made use of when the seeds germinate. It is 

 dissolved with formation of corrosion canals, and finally only the 

 middle lamella between adjoining cells of the parenchyma is left. 



119, Inulin. 



Inulin is particularly abundant in the underground organs of 

 many Composites. It occurs in solution in the cell-sap, and 

 functions as n on -nitrogenous reserve material. If some inulin is 

 treated with cold water, it is found to dissolve with some difficulty. 

 If, however, we apply heat, the inulin completely dissolves. Inulin 

 is unable to reduce Fehling's solution. If, however, we treat hot 

 Fehling's solution with a solution of inulin prepared by heating, 

 a separation of small quantities of Cuprous oxide does take place, 

 owing to the fact that hot water of itself is able to convert small 



