OF MICROSCOPIC OBJECTS. 121 



dried, burn it upon thin glass until all appears white, when 

 it must be carefully mounted in balsam. I think, however, 

 it is better to leave it in strong acid until all the substance, 

 except the required portion, is removed ; but this will take 

 a length of time, varying according to the mass of the 

 plant. Of course, when this latter method is used, the 

 skeleton must be washed from the acid, &c., before being 

 mounted in balsam. 



These siliceous cuticles are readily found. The straws of 

 most of the cereals, wheat, oat, &c. ; the JiusJes, also, of some 

 of these ; many canes ; the equisetum, as before described ; 

 and some of the grasses. Many of these are everywhere 

 procurable, so that the student can never want material for 

 a splendid object for the polariscope. 



In Chapter III. the scales (or hairs) which are often found 

 upon the leaves of plants were mentioned as beautiful objects 

 when mounted dry; but some of these when detached from 

 the leaf which is easily done by gently scraping it, when 

 dried, with a knife present brilliant starlike and other 

 forms, if mounted in balsam and used with the polariscope. 

 There is a little danger, when placing the thin glass upon 

 the balsam, of forcing out the scales in the wave of matter 

 which is always ejected ; this may be overcome by applying 

 to the slide, previously to placing the objects upon it, an 

 extremely thin covering of balsam diluted with turpentine 

 as before mentioned, letting it dry more or less with the 

 objects placed in it, and then, after the addition of a little 

 more balsam, putting the cover on, and thus giving them 

 every chance of adherence; or by using the balsam with 

 chloroform, as before noticed. This method is peculiarly 

 successful in cases where it is desired to arrange several 

 objects symmetrically on a slide, and to obviate their sub- 

 sequent disturbance by placing the cover on. Type slides 

 with several parts of an insect displayed upon them, scales 

 of fish, or of plants, &c., may thus be shown, so that the 

 number of slides may by this plan be seriously diminished. 



