32 PRACTICAL BOTANY 



Another method which gives good results, especially in 

 clearing growing-points, is by the use of " eau de javelle " (see 

 Appendix A). The object, either fresh, or after hardening in 

 alcohol or picric acid, is mounted under a cover-slip in " eau 

 de javelle " for three or four, to ten or fifteen minutes, accord- 

 ing to the rapidity of action of the reagent : very gentle 

 warming over a spirit-lamp will quicken the action : it is then 

 to be carefully washed with water, next with dilute acetic acid, 

 and it may finally be mounted in glycerine. 



All the above-methods involve \hzpartial or complete dis- 

 organization of the protoplasmic body : the following method of 

 treatment has the advantage of preserving the structure of the 

 protoplasm and of the nucleus, and it is specially applicable 

 to material in which the protoplasm has been fixed by alcohol, 

 or by picric acid and alcohol. The sections (after staining, if 

 that is considered necessary) should be placed for a few 

 minutes in absolute alcohol ; they should then be transferred 

 to a watch-glass, containing either a mixture of turpentine and 

 creosote (four parts of the former to one of the latter), or some 

 oil of cloves ; sections which have been stained with aniline dyes 

 are best cleared by cedar-wood oil ; they should be left in the 

 clearing agent for a short time, until they appear to be quite 

 transparent, and should then be mounted in a drop of Canada 

 balsam or Dammar. 



Permanent Mounting. It was pointed out in the previous 

 chapter that objects mounted in water cannot easily be kept, 

 while the objects do not appear so transparent in water as in 

 some medium of higher refractive index. The media most 

 commonly used are glycerine, glycerine jelly, Canada balsam, 

 and Dammar. 



Glycerine. This may be used for objects prepared from fresh 

 material, or hardened with alcohol, &c., and is especially suited 

 to objects stained with ammoniacal solution of haematoxylin, 

 carmine, and many of the aniline colours : it is also used for 

 objects cleared by potash, or " eau de javelle." Dilute glycerine 

 should be used for this purpose, consisting of a mixture of 

 pure glycerine with an equal bulk of water. 



In order to make the preparations mounted in glycerine per- 



