AND HOW TO USE IT. 189 



for comparison. He will observe the striking difference between 

 the two substances, and see how easy it is to distinguish one from 

 the other. Thus, whilst in coffee the cells are small and more or 

 less angular, chicoij-cells present a round or oval outline ; the 

 presence of dotted duds will also be detected, which are entirely 

 absent from coffee. To make the comparison complete, a coffee 

 berry should be soaked in water until the skin, or seed coat, 

 becomes loosened. A portion of this is then, with the point of a 

 knife, to be removed to a slide and examined in glycerine, when 

 it will be found to consist of a hyahne membrane in which are 

 imbedded small, rod-like bodies of elliptical shape, and having 

 their long axes running in the same direction. These rods 

 cannot be mistaken for any of the ducts met with in chicory. 



Orange Peel, common object though it be, is not to be 

 despised by the microscopist. Transverse sections must be 

 prepared by the gum method. These sections are not to be 

 subjected to the action of alcohol ; but after drying between 

 glass slips, soak them in turpentine and mount in balsam. We 

 shall then have a good view of the large globular glands whose 

 office it is to secrete the essential oil, upon which the odour of the 

 orange depends. Sections may also be bleached, and stained 

 with carmine and aniline green as before mentioned. 



Potato. — From the large amount of water which it contains 

 thin sections cannot be cut from the potato in its natural state. 

 It. must, therefore, be partially desiccated, either by immersion in 

 methylated spirit for a few days, or by exposure to the air. 

 Sections may be readily obtained by imbedding and cutting in 

 paraffin. Such sections, mounted in balsam, are very beautiful, 

 the starch being seen in situ, whilst if polarised light be employed, 

 each granule gives its characteristic black cross. 



Rush is to be prepared and cut as orange peel. Transverse 

 sections of this plant furnish slides of most exquisite beauty. 



Sponge may readily be cut after being tightly compressed 

 between two pieces of cork, or its interstices may previously be 

 •filled up by immersion in melted paraffin or mucilage, and 

 sections cut in the usual manner. 



Vegetable Ivory, after prolonged soaking in cold water, 



