4 2 BOTANICAL MICROTECHNIQUE. 



weight of gelatine is soaked in six parts of water ; seven 

 parts of pure glycerine are then added, and finally a gram of 

 phenol to each 100 grams of the mixture. The whole is 

 then warmed for 10 to 15 minutes with constant stirring, 

 until the fluid is quite clear, and is finally filtered through 

 glass wool or filter-paper. This may evidently be best done 

 with the aid of a hot-water filtering apparatus. 



57- Less delicate objects, like sections of wood and the 

 like, may be transferred directly from water to glycerine- 

 gelatine ; more delicate preparations should first be brought 

 into glycerine. This may be accomplished, in case of 

 objects which collapse very easily, by placing them in a \Q% 

 solution of glycerine, which is then allowed to concentrate 

 gradually by standing in the air. 



58. Since the glycerine-gelatine (glycerine jelly) is solid at 

 ordinary temperatures, it must be warmed before use until 

 it becomes fluid ; and for this purpose the paraffine bath 

 may be used ( 47). Or one may prepare small pieces of the 

 jelly, each of suitable size for one preparation, and melt 

 them upon the slides. Such pieces may be readily prepared 

 by allowing a quantity of the jelly to harden upon a plate 

 in a thin layer, which is then cut into blocks. 



59. If annoying air-bubbles occur in the preparation en- 

 closed in glycerine-gelatine, they can be easily removed from 

 objects not too delicate by heating the jelly to boiling. 



Since preparations in glycerine-gelatine usually shrink 

 pretty strongly when kept for a long time, it is generally 

 advisable to seal them with a cement ring ; but it is best, 

 especially with thick sections, to apply this ring after some 

 time, as otherwise the cover-glass is easily broken by the 

 subsequent concentration of the jelly, and it is easier to 

 remove by warming, any air-bubbles that may appear. For 

 demonstration preparations I apply the cement only after a 

 year. 



5pa. Chloral-hydrate gelatine is recommended by Geoffroy 

 (I) as a mounting medium. It is prepared by dissolving 3 

 to 4 grams of good gelatine in 100 ccm. of a 10$ aqueous 

 solution of chloral hydrate, at as low a temperature as pos- 



