PRACTICAL HINTS 



companion. When available a condensing lens is useful to throw 

 a brilliant spot of light upon the wood, and in all cases the 

 surface should be moistened, as the wetting emphasizes certain 

 parts by deepening their colour and throwing them into relief. 

 With the solid wood such stains as are commonly employed by 

 microscopists seldom yield good results, as even when they 

 single out certain kinds of tissue and avoid others there is sure 

 to be some different kind in the next layer beneath which 

 brings the whole back to a uniform colour. Nevertheless 

 Perchloride of Iron may be employed to advantage, as it some- 

 times shows up the rays of certain species. 



When a good idea of the general structure has been obtained 

 by means of the lens, the microscope may be used. A low 

 power is sufficient, as, for instance, a two-inch Swift, which will 

 show the shape of the pores and rays, and will serve to measure 

 them and to count their number. 



Seen under the microscope by reflected light, a piece of wood 

 is a beautiful object, and some of the coloured woods, such as 

 Mahogany, are most brilliant and even gorgeous, for the play of 

 colour from the resin or gum, and the different hues of the various 

 kinds of tissue are most agreeable to dwell upon. 



For low powers I use a simple contrivance consisting of a 

 tube some ten inches long, fitted to receive an ordinary microscope 

 eye-piece at one end, and reduced to take the objective at the 

 other. Upon the lens or lower end is lightly telescoped a 

 piece of tube, some five inches long, of which one side, to the 

 length of two inches, is removed to allow the light to fall upon 

 the wood. This outer tube is to regulate the distance be- 

 tween the lens and the wood, so that by resting it upon the 

 surface the latter is immediately brought into focus. The 

 advantage of this simple apparatus is that any block of 

 wood can be examined without the trouble of reducing it to 

 a size small enough to go on to the stage of a microscope. 

 Besides it is not always convenient to cut a specimen, so 

 that this is a practically indispensable form of instrument, if the 

 specimens in a museum are to be examined microscopically. 

 A minor recommendation is that it can be slipped into the 

 pocket. I need not touch upon the use of the higher powers of 

 magnification, for although they are no doubt essential in describ- 

 ing the structure, they are by no means so in recognizing it, and 

 I wish to impress upon my readers most strongly that they need 

 not be deterred from this study by the feeling that the work needs 

 special training, for the pocket lens will carry them along for 

 nine-tenths of the road, and for the most part they need not use 

 the microscope at all, though I promise them that the fascination 

 of the work will soon lead them to employ it. If so small a 



XXXV 



