168 MOSSES AND LIVEEWOETS 



entangled in the teeth of a peristome. Very often, 

 after chasing a number of these bubbles, one sees 

 one of them left, possibly almost hidden by the 

 leaves, or at the bottom of a capsule, where it 

 would seem to be practically powerless for mischief ; 

 and one is tempted to let it alone, but experience 

 will sooner or later show that it is a great mistake 

 to do so. I have had many a slide ruined by just 

 such a bubble working its way up to the surface, 

 and this even years after the mounting was done. 

 It is far better to make a rule that, rather than 

 allow a serious blemish of this kind to remain, the 

 slide must be sacrificed, and the mount be recom- 

 menced. It will be found advisable in many 

 cases, especially where an object likely to retain 

 air is under treatment, to put it direct from the 

 preparatory fluid into a little liquid jelly on a 

 spare glass slip (I generally use one with a 

 " sunk cell " for this purpose), and then to extract 

 the air before transferring it to the slip on which 

 it is to be mounted. The whole thing thus becomes 

 more or less saturated and covered with the jelly, 

 and the air is not so likely to reappear among 

 the leaves as where the whole process is carried 

 out on one slip. If this course is adopted, a 

 second hot-water bath will be required, in order 

 to prevent the jelly on one slip cooling while the 

 other slip is in .course of preparation. 



When the specimen is thus in place, immersed 

 in plenty of the liquid jelly, the cover-glass is 



