38 PRACTICAL BOTANY 



The above reactions of cellulose may with advantage 

 be repeated in sections cut from the endosperm of the 

 common Date. Take the " stone " of a dried Date, and 

 clearing away with a scalpel the brown superficial coat, 

 so as to lay bare the pearly endosperm, cut thin sections 

 in a tangential plane, i.e. parallel to the external 

 surface. Very small sections will suffice, and great care 

 should be taken to cut the sections thin, otherwise the 

 razor will be damaged, and the sections will not answer 

 their purpose. It would be well to use only a small 

 part of the edge of the razor for this work, e.g. the part 

 nearest the heel of the blade. 



Examination first under a low, and then under a high 

 power, will show the mass of homogeneous tissue of the 

 endosperm as consisting of thick, highly refractive 

 cell-walls forming a network with circular meshes : 

 here and there the cell-walls show thin spots the 

 pits. The circular cavities are occupied by granular 

 protoplasm. The thinnest parts of the sections will 

 show the reactions the best, and the superficial 

 layers of the thick cell-walls better than the middle 

 lamella. 



B. Lignified Walls. 



For the reactions of ligriified walls the wood of the 

 Pine will serve : for instance, sections may be cut from 

 an ordinary wooden match. Having cut thin transverse 

 sections, soak them first in alcohol to remove bubbles 

 of air : mount one of them in glycerine, and observe 

 under a high power the very regular network of cell- 

 walls, which are of almost uniform thickness, and are 

 colourless or slightly yellow : protoplasm is practically 

 absent in this tissue. 



