416 SECTIONS OF STEMS AND ROOTS. 



already given (§ 137) leave little to be added respecting this 

 special class of objects ; the chief points to be attended-to being 

 the preparation of the Stems, &c. , for slicing, the sharpness of the 

 knife and the dexterity with which it is handled, and the method 

 of mounting the sections when made. The Wood, if green, should 

 first be soaked in strong Alcohol for a few days, to get-rid of the 

 Resinous matter; and it should then be macerated in Water for 

 some days longer, for the removal of its Grum, before being sub- 

 mitted to the cutting-process. If the Wood be dry, it should first 

 be softened by soaking for a sufficient length of time in Water, 

 and then treated with Spirit and afterwards with Water, like 

 green wood. Some Woods are so little affected even by prolonged 

 maceration, that boiling in water is necessary to bring them to the 

 degree of softness requisite for making sections. No Wood that 

 has once been dry, however, yields such good sections as that 

 which is cut fresh. When a piece, of the appropriate length, has 

 been placed in the grasp of the Section- in strument (wedges of deal 

 or other soft wood being forced-in with it, if necessary for its firm 

 fixation), a few thick slices should first be taken, to reduce its 

 surface to an exact level ; the surface should then be wetted with 

 Spirit, the Micrometer-screw moved through a small part of a 

 revolution, and the slice taken off with the razor, the motion given 

 to which should partake both of drawing and pushing. A little 

 practice will soon enable the operator to discover, in each case, 

 how thin he may venture to cut his sections without a breach of 

 continuity ; and the Micrometer-screw should be turned so as to 

 give the required elevation. If the surface of the Wood has been 

 sufficiently wetted, the section will not curl-up in cutting, but will 

 adhere to the surface of the Razor, from which it is best detached 

 by dipping the razor in water so as to float away the slice of wood, 

 a camel-hair pencil being used to push it off, if necessary. All 

 the Sections that may be found sufficiently thin and perfect, should 

 be put aside in a bottle of weak Spirit until they be mounted. 

 For the minute examination of their structure, it is generally best 

 to preserve them in fluid ; and no fluid answers better than weak 

 Spirit. Where a mere general view only is needed, Dry-mounting 

 answers the purpose sufficiently well ; and there are many Stems, 

 such as the Clematis, of which Transverse Sections rather thicker 

 than ordinary make very beautiful Opaque objects, when mounted 

 dry on a Black Ground. Glycerine-jelly answers very well for 

 most Sections ; but Canada Balsam should not be had recourse to 

 except in the case of very opaque sections, as it usually makes the 

 structure too transparent. Transverse sections, however, when 

 slightly charred by heating between two plates of Glass until they 

 turn brown, may be mounted with advantage in Canada Balsam, 

 and are then very showy specimens for the Solar or Gas-Microscope. 

 The number of beautiful and interesting objects which may be 

 thus obtained, at the cost of a very small amount of trouble, can 



