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have specimens of tlie same kind of leaves dyed iu all tlu'ee 

 colours and mounted botli ways, or only the blue dyed one in 

 balsam or dammar. Leaves or sections wbicli are to be mounted 

 in Deane's medium should, after the final -washing, be put into 

 the following solution for about two days, as directed by Mr. 

 Deane: — Rectified spirit 1^ ounces; pure water, 1^ ounces; 

 pure glycerine 5 drams. Take the tissues out of the above 

 fluid, di-ain off as much as possible, and mount in the medium. 

 I prefer this way of mounting for most leaves, for this reason, 

 it does not make the leaves so very transparent as dammar or 

 balsam does, and generally every cell wall is distinctly seen, the 

 crystals, the hairs, and every other part of the leaf. Leaves to 

 be mounted in dammar or balsam should be thoroughly di-ied 

 from the last washing, after dyeing ; this is best done by put- 

 ting them in one of the interleaved books before mentioned 

 for a day or two, and when thorouglily dry take them out and 

 put them into a small wide-moutlied bottle, and pour over 

 them benzine enough to cover them (benzine coUas is much the 

 best), and leave them to soak till perfectly transparent, then 

 take them out, di-ain, but not dry, and mount quickly in the 

 balsam or dammar dissolved in benzine. Leaves mounted in 

 this way are beautiful objects for the polariscope if they con- 

 tain crystals or have any hairs upon them, but they are nearly 

 always so transparent that the cell walls are cxuite obliterated. 

 Good leaves to experiment upon are chickweed, mercury, and 

 wild strawberry, for sjihteraphides. For long crystal prisms, the 

 outer skin of the gladiolus bulb, sweet orris root, and leaves 

 of the blue flag, also the outer skin of garlic and onion. For 

 short prismatic crystals, clover, sanfoin, beech, and trefoil. For 

 true raphides, squiU bulb, leaf of hyacinth, blue bell, lemna 

 trisulca, balsams, willow herb, fuchsia, evening primrose, and 

 arum. Cystoliths. — Leaves containing these shoidd not be 

 mounted in dammar or balsam, as they do not polarise, and are 

 generally rendered invisible by this way of mounting. No one 

 need be afraid of not getting specimens, for I believe the greater 

 part of our plants contain crystals of one kind or other, and they 

 may be well and easily studied in situ 'by mounting in Deane's 

 medium, after properly preparing and dyeing, but they may be 

 often very well seen by simply bleaching, washing, and examin- 

 ing in water. And I may add that the crystals afford an abun- 

 dance of beautiful materials for the microscope, and that the 

 more they are studied the more they wiU be admired. Their 

 taxonomic and ohysiological significance too is an important 

 subject for further research, concerning v/hich Prof essor Gulliver 

 has given the results of extensive observations. He recommends 

 boiling the plant tissues in a solution of caustic potass ; this is 

 an easy way of exposing the crystals and their cells, though 



