APPENDIX A 517 



tied cells resist its action (see p. 39). It is used with cane-sugar, 

 as a test for proteids, and a few drops of it are added to a solution 

 of aniline sulphate as a test for lignin. 



It may also be used as a solvent for crystals of calcium oxalate 

 (p. 178). 



Turpentine is used with creosote, or carbolic acid, as a clearing 

 agent before mounting in Canada balsam (p. 52). 



Water may be used as a mounting medium (p. 24), and as a 

 solvent for various reagents ; it may also be used for the cultivation 

 of small organisms, or pollen-grains, spores, or Fungi, under the 

 microscope, and for this purpose a moist chamber is to be con- 

 structed as follows : 



A piece of thick rough cardboard is cut to the size of the glass 

 slide, and a circular hole is punched out of the middle of it of 

 such a size as to be completely covered by a cover-slip. The piece 

 of cardboard is then soaked in water (or boiled in water when pure 

 cultures of Fungi are to be made), so as to saturate it, and placed 

 on the glass slide. A drop of water (or solution as described 

 below) is placed on the cover-slip, the object is immersed in it, 

 and the cover-slip is then inverted over the hole in the piece of 

 cardboard. Thus the object is suspended in a drop of liquid on 

 the under surface of the cover-slip. Any loss from the chamber 

 by evaporation is prevented by occasionally wetting the cardboard 

 on the slide with freshly boiled, distilled water. 



The liquid to be used will of course vary with the nature of 

 the object to be observed. In the case of Alga3, water may be 

 used ; in the case of Fungi, decoctions of various organic sub- 

 stances (fruits, animal tissues, &c.), or a solution of sugar, accord- 

 ing to the ha.bit of the Fungus. For observing the germination 

 of the spores of Mosses and Ferns, water will suffice ; but in the 

 case of pollen-grains a solution of sugar is necessary (1-20 or 

 even 30 per cent., the concentration being different for different 

 plants) (p. 202) ; for observing the process of cell-division in the 

 hairs on the stamens of Tradescantia, a 2 per cent, sugar-solution 

 may be used (p. 84). 



White of Egg is sometimes used as an embedding medium 

 (see p. 12). 



