PREPARING SPECIMENS. 91 



cerine jelly or Dean's gelatine, it should be soaked in a 

 preparatory fluid, otherwise these mediums will not properly 

 permeate the specimen. The preparatory fluid is made as 

 follows : 



Rectified spirits, ij ounce. 



Distilled water, ij ounce. 



Glycerine, 3 fluid drachms. 



Mix, and keep in readiness. A drop of this fluid is placed 

 on the .object, which may then be put away under a bell 

 glass for one or two days. As the spirits and the water 

 evaporate, the glycerine will take their places in the cellu- 

 lar tissue of the specimens. When pure glycerine is used, 

 the specimens are better if soaked for a time in glycerine 

 before being permanently mounted, so that all water con- 

 tained in the object may be thoroughly displaced by the 

 glycerine. 



When the object has been well soaked in the preparatory 

 fluid, it may then be mounted in either Deane's gelatine 

 or glycerine jelly, the former medium being the best. All 

 the superfluous fluid must be drained away, the glass slip 

 and cover glass warmed. The gelatine may be melted by 

 placing the bottle in which it is contained in a little hot 

 water for a time. When melted, a drop should be placed 

 on the object, the cover glass should then be gently breathed 

 upon and carefully placed on the drop of the medium, and 

 when this is thoroughly set, a ring of the white zinc cement 

 should be put round the cover glass to fix it to the glass slip 

 and also to prevent evaporation. The slide may then be 

 labelled, numbered, and put away. 



The peristomes of mosses also form beautiful as well as 

 instructive objects. These should be mounted dry in most 

 cases, although in some of the smaller capsules the whole 

 capsule, with its peristome, may be mounted in one of the 

 mediums above mentioned. My usual plan, however, is to 

 mount these peristomes in a cell sufficiently deep to allow a 

 cover glass to be affixed without injury to the object. The 

 vulcanite rings serve, but are apt to warp, and so come off 

 the slide later on. The glass cells are best, but are very 



