SECTIONS OF STEMS. 387 



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 gum, before 

 being submitted 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 afterw r ards with water, 

 like green wood. Some woods are so little affected even by 

 prolonged maceration, that boiling in water is necessaiy to 

 bring them to the degree of softness requisite for making sec- 

 tions. 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- 

 instrument (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 

 oif 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 much better to preserve them in fluid, than to mount 

 them either dry or in Canada balsam; and no fluid answers 

 better than weak spirit. Where a mere general view only is 

 needed, the dry mounting answers the purpose sufficiently well. 

 It is only in the case of the section being unusually opaque, that 

 mounting it in Canada balsam can be of any service whatever; and 

 in general it is rather injurious than useful, making the section 

 so transparent that its features can scarcely be discerned. Trans- 

 verse sections, however, when 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 scarcely be conceived save by 

 those who have made a special study of these wonderful struc- 



