APPENDIX A 509 



coloration is removed from all parts excepting the corky and 

 cuticularized walls. 



Glycerine is the most generally used medium for mounting, 

 as it has the advantages of a high refractive index, and of not 

 being subject to evaporation. It may be applied either pure or 

 diluted : pure glycerine is to be used, after hardening in alcohol, 

 when it is desired to observe the details of the protoplasm, e.g. 

 in the preparation of the contents of the embryo-sac (p. 204) ; 

 dilute glycerine (1 part glycerine, 1 part water), is however, of 

 most general use. 



Glycerine Jelly is a suitable mounting medium for many 

 objects (p. 52) : it may be bought ready for use from dealers in 

 microscopic requisites ; or it may be prepared according to Kaiser's 

 receipt, as follows : 1 part by weight of finest French gelatin 

 is to be soaked for about two hours in 6 parts of distilled water : 

 7 parts of chemically pure glycerine are added, and to about 100 

 grammes of this mixture 1 gramme of carbolic acid is added. 

 The whole mixture is to be warmed and continually stirred for 

 10-15 minutes, till the fluid is clear, and then to be filtered 

 through glass-wool. 



Gold Chloride is sometimes used in a 1-0 per cent, or 0'5 per 

 cent, solution in water as a delicate stain for protoplasm. 



Gold-Size is to be obtained from dealers in microscopic requi- 

 sites : it is used for sealing up slides, and a layer of it may with 

 advantage be applied after sealing with asphalte, or Brunswick 

 black. 



Gum Arabic is occasionally used as an embedding medium for 

 very small objects (p. 12). 



Hsematoxylin. A number of preparations of this colouring- 

 matter are in use ; of these the following are those generally 

 employed for vegetable tissues : 



1. Alum Solution of Heematoxylin. Dissolve 0'35 gramme of 

 hceraatoxylin in 10 c.c. of water, and add to it a few drops of a 

 solution of alum consisting of 1 gramme of alum to 10 c.c. of 

 water. 



2. Kleinenberg's Hsematoxylin. Saturate some 70 per. cent, 

 alcohol with calcium chloride ; let the mixture stand for twelve 

 to twenty-four hours over alum, shaking occasionally ; add 8 



