APPENDIX ON PRACTICAL WORK. 1 59 



action by turning a screw at the back of tbe tube frame. A good light 

 is, of course, necessary. Now remove the low power and follow the 

 same course with the high one. A higher magnification can be effected 

 by pulling out the inner part of the microscope tube further than the 

 groove. 



(2.) Objects when viewed by transmitted light require more elaborate 

 treatment, and the following additional apparatus will be required :— 

 (a.) A razor for section cutting. A shilling army-razor will answer 

 perfectly well. (b.) Some pieces of elder pith, (c.) Half a dozen watch- 

 glasses, (d.) A small camel' s-hair brush, (e.) Half a pint of methylated 

 spirit, an 8-oz. bottle of glycerine, and the following reagents put up in 

 i-oz. phials, through the corks of which pieces of glass rod are passed 

 (any chemist will do this) : — Dilute glycerine (half glycerine, half water), 

 iodine solution (dilute the liquor iodi of chemists to a dark-sherry colour), 

 magenta solution (Judson's magenta dye diluted to port-wine colour), 

 caustic potash solution (five per cent.), and strong sulphuric acid. 



Take, for example, a small piece of a delicate leaf treated with chloral 

 hydrate, a daisy floret torn open, some pollen, or a bit of epidermis 

 pulled from the lower surface of a geranium leaf. Now, with a glass 

 rod place a small drop of dilute glycerine in the centre of a slide, put 

 the object in the drop, and cover with a cover-glass. One edge of this 

 should first be made to touch the slide, and the glass then gently lowered 

 with a mounted needle. Now proceed as before, 1 tut, in addition, turn 

 the mirror so as to reflect light upwards through the object. N.B. — 

 Perfect cleanliness is necessary in all microscopic work. The microscope 

 lenses should be kept clean with a piece of new wash-leather, while 

 cover-glasses are cleansed by rubbing them gently with a piece of old 

 silk between the thumb and forefinger. Of course they should first be 

 washed in water if smeared with glycerine, &c. 



Transmitted light is most useful for thin sections of root, stem, leaf, 

 anther, ovary, &c. These should be preserved in methylated spirit, and 

 placed in a half and half mixture of this and glycerine for twenty-four 

 hours before required. Small objects may be held in a slit in a piece 

 of elder pith, while leaves can be rolled up. There is no royal road to 

 section cutting, and nothing but practice will give the requisite skill. 

 A few hints may, however, prove useful. Hold the object firmly in the 

 left hand, and, grasping the middle of the razor firmly with the right, 

 its edge away from you, make a steady diagonal sweep from the base of 

 the blade. Do not push or saw. The razor should be kept wet with 

 water for fresh objects, with spirit for spirit specimens. With a sharp 

 razor the weight of the blade should be sufficient to carry it through if 

 a slight swing is given. Many prefer to cut towards them, using the 

 first finger of the left hand as a support for the razor-blade. A number 

 of sections should be made, and placed in a watch-glass containing dilute 

 glycerine. From this the thinnest can be picked out with the brush and 

 mounted as before. A piece of black paper placed beneath the watch- 

 glass will enable the sections to be seen more clearly. Do not be con- 

 tented till your sections are so thin that the cover-glass will lie quite 

 flat, and so transparent that all the details can be made out with the 

 high power. 



In many cases sections are made clearer by staining, since different 

 elements are affected differently. This process is conveniently effected 



