BOTANICAL TECHNIQUE 635 



flood with solution A and stand the slide on end to drain and dry. 

 Harden in 70 per cent, alcohol for several minutes and transfer 

 rapidly through 1)5 per cent, alcohol into carboxylene or xylol. 

 Leave for several hours and thereafter bring to water. 



Collodion sections are usually mounted by the albumen method 

 (§ 216), ether method (§ 217). or by arranging the sections on the 

 slide, gently pressing them and then pouring a little clove oil 

 over them. 



1261. Mounting Media. Most commonly used are : 1. Aqueous 

 mountants, viz. water, glycerin (pure or diluted), lactic acid, 

 glycerin jelly, Amann's lactophenol, 4 per cent, aqueous formalin, 

 2 per cent, aqueous acetic acid, Keefe's or Evan's or other fluids 

 that preserve a green colour (but omit any alcohol) and glycerin 

 saturated with zinc iodide. See also Weston, Science, Ixx, 

 1929, p. 455 (modifled Amann). Aqueous media are satisfactory 

 if the cover is sealed to the slide with a cement. For material 

 of some thickness build up a cell of several well-dried coats of 

 cement and seal the cover to this. 



Calcareous material (Chara, etc.) must not be sealed in media 

 containing acids. Mount living marine algae in media made up 

 with sea -water. 



2. Non-drying oils, viz. paraffin oil or white mineral oil (after 

 dehydration and clearing), castor oil, linseed oil, olive oil ; oil of 

 wintergreen does not require clearing. 



3. Resinous media, viz. Canada balsam, gum damar, thickened 

 cedar oil, Venetian turpentine, euparal. Styrax, tolu balsam and 

 synthetic resins of high refractive index (see Hanna, Science, 

 Ixv, 1927, pp. 41 and 575 ; ihid., Ixx, 1929, p. 16 ; Journ. Roy. 

 Micr. Soc, 1, 1930, p. 424 ; Needham, Journ. Am. Pharm. Assoc, 

 xiii, 1924, p. 424) are most useful for diatoms. 



Other mounting media are : — 



Potassium silicate (Raybaud, Rev. Gen. Bot., xxxvii, 1925, 

 p. 511) ; it is hard on most stains ; material can be mounted 

 direct from alcohol. 



Sodium silicate (Nitzulescu, C. R. Soc. Biol., Ixxxix, 1923, 

 p. 1065). 



Refer also to Chapter XXI. 



1262. Sealing Mounts. Damar balsam, gold size and Venetian 

 turpentine are most commonly used. A mixture of gum mastic 

 and paraffin (Lagerhein, Bot. Not., 1902 ; see also Thomas, New 

 Phyt., X, 1911, p. 105) is applied by means of a heated thick 

 copper wire. Powder the mastic and heat cautiously in a porcelain 

 dish until melted ; add the paraffin in small pieces and stir with a 

 piece of wood until homogeneous and free from lumps. This seal 

 is easily removed with a knife. 



Pulverised gum tragacanth (Neumann and Hueber, Zcit. 

 wiss. Mik., xliv, 1927, p. 322) and Duco (Mitchener, Stain 



