180 MOSSES AND LIVERWORTS 



stands well above the sides of the cell, and the 

 object is lowered into it. The cover-glass must now 

 be poised between the finger and thumb, and, after 

 being brought as near as possible to the solution 

 without touching it, allowed to fall into place on 

 the top of the cell, driving the superfluous solu- 

 tion out as it settles down. Sometimes, and more 

 particularly if too little of the solution has been 

 used, an air-bubble will make its way in at the 

 last, and then the cover-glass must be quickly 

 raised on one side, and some additional solution be 

 introduced before it is allowed to fall again. The 

 cover-glass is now gently pressed down onto the 

 marine glue with a mounting-needle, and after 

 being carefully wiped, so as to free it from all traces 

 of the solution, is ringed round with the marine 

 glue medium, and later on with a spirit varnish. 

 The whole may then be finished off with asphalt 

 varnish. Should it be desired to mount a thicker 

 object, such as a piece of a plant, or some of the 

 larger capsules, a cell of vulcanite must first be 

 attached to the slip by marine glue, and the above 

 steps then followed. The chief advantages attend- 

 ing this method (in addition to the excellent 

 nature of the medium as a preserving agent) are, 

 that no special preparation of the object is neces- 

 sary, and that the process needs no application of 

 heat. On the other hand, it is subject to all 

 the drawbacks incidental to the use of a liquid 

 medium, which have already been generally re- 



