12 PRACTICAL BOTANY 



spirit-lamp in a small tinned iron spoon, is poured 

 into the cavity so as to surround and cover the 

 object. 



If the object be small it will be found convenient to 

 heat one end of a thick copper or platinum wire, and 

 with it melt a small cavity, in which the object may be 

 placed in such position as is found convenient. 



The sections must not be made until the paraffin is 

 quite cold, and firmly set. 



It is important to keep the embedded objects wet 

 with alcohol during the process of cutting, in order to 

 prevent the drying-up of the object, and its consequent 

 contraction away from the substance in which it is 

 embedded. 



Another method of embedding is to moisten the object in 

 water, and then suspend it by means of a thread in some white 

 of egg, which has been previously well shaken up, and then 

 strained through muslin. The white of egg should be in an 

 evaporating dish. The object should be left thus suspended for 

 some hours, so that the white of egg may come into close contact 

 with all parts of it. Heat is then applied by means of a water- 

 bath, and the white of egg coagulates. The part surrounding 

 the object is now cut out and hardened in alcohol for some days. 

 This method is useful for making sections of buds and flowers. 



A third method of embedding may be employed when it is 

 desired to obtain sections of very small objects, such as spores, 

 pollen-grains, &c. A thick layer of strong clean gum is laid on 

 the flat surface of a piece of pith ; this is allowed to become 

 nearly dry ; and then the pollen-grains or spores are dusted on to 

 it ; they are then covered with another thick layer of gum, and 

 the whole is allowed to dry. Sections are now made of the dried 

 gum, and on their being placed in water or weak glycerine, the 

 gum is dissolved, and the sections of the pollen-grains or spores 

 are set free. 



