Crystals and Polariscope Objects 203 



all over the surface of the cover, and put away, protected 

 from dust, until quite dry ; then add a drop of Canada 

 balsam, and mount in the ordinary way. 



Starches may also be mounted in glycerine jelly (see 

 Lesson VIII.), but they do not polarize so well as the balsam 

 preparations. 



Sections of Starch-bearing Tissues. — The stems, roots, 

 and bulbs must be hardened in methylated spirit for a 

 week; then make transverse or longitudinal sections. 

 Dehydrate in methylated spirit, clear in clove-oil, and 

 mount in Canada balsam. 



Cuticles containing Raphides. — The most common are 

 taken from the following bulbs: garlic, onion, lily, hyacinth. 

 Strip off the cuticle from the fresh specimen ; dehydrate in 

 methylated spirit, clear in clove-oil, and mount in Canada 

 balsam. 



Cuticles of Leaves. — Cut up the leaf into small 

 pieces, and soak in water until rotten ; the cuticles can 

 then be separated, washed in water, dehydrated in methy- 

 lated spirit, cleared in clove-oil, and mounted in Canada 

 balsam. 



Cotton, Hemp, Wool, Silk, Flax, etc. — Place the fibres 

 in methylated spirit to dehydrate ; then clear in clove-oil, 

 and place a little on a slide. Separate the fibres from each 

 other with needle-points ; apply a few drops of Canada 

 balsam and a cover-glass. 



Scales of Leaves. — Scrape the leaf with a knife, and 

 put the scrapings into a bottle of turpentine, and soak until 

 all trace of air has disappeared from the scales ; then pour 

 off the turpentine. Take up a little of the scales on the 

 point of a penknife, and mount them in Canada balsam in 

 the ordinary way. Some leaf-scales are very difficult to de- 

 prive of air ; in fact, it is impossible to get them quite free. 



The following animal tissues make good polariscope 

 objects : fish scales, palates of molluscae, sections of hairs 

 and quills, horns and hoofs, whalebone, claws of dogs, cats, 

 and fowls, decalcified bones, muscular tissues. 



