296 PRACTICAL MICROSCOPY. 



place a small drop of Farrant's medium in the centre, to 

 which is attached a portion of the substratum bearing the 

 fungus upon it. The slide must now be placed under the 

 desiccator until perfectly dry, when the thin covering glass 

 should be placed on in the manner already described, and 

 finished in the usual way. 



There is another style of mounting it may be useful to 

 describe, i. e. in such a manner that the Lieberkuhn may be 

 used with the slide, to produce illumination on a dark 

 ground, so that such objects as Foraminifera or the pollen 

 of the mallow may be viewed with this appliance, as an 

 opaque object 



Take a very shallow varnish cell slip, but deep enough 

 of course to contain the object, and turn upon the centre of 

 it a disc of Bate's dead-black varnish, allow this to dry and 

 become well aged. When proceeding to mount, say the 

 pollen of Althea roses (Fig. 97), dust it over this blackened 

 disc, place in the desiccator until dry, and then put on the 

 cover in the usual manner. If the pollen be dusted over 

 the whole of the circle, the observer will be able to use 

 the slide both as a transparent and opaque object. Many 

 preparations, such as the disc of deal, do not require fixing 

 either to the cell or its cover, and this class of objects 

 requires no special directions for successful mounting. 



MOUNTING IN GUM RESINS. Objects required for 

 mounting in gum resins need of course quite as much 

 preparation as when put up by the dry method ; but that 

 we are about to describe is perhaps the best suited for 

 beginners, as the gum resins are good preservatives, and 

 the preparations are likely to be permanent with the 

 minimum amount of care. 



Canada-balsam has been used for a long period for this 

 style of mounting, either by itself or when diluted with 

 chloroform or benzol. 



