76 MODE OF PREPARING PLANTS FOR EXAMINATION. 



APPENDIX, CONTAINING AN ACCOUNT OF THE MODE OF PREPARING 

 RECENT AND FOSSIL PLANTS FOR MICROSCOPIC EXAMINATION. 



Slices of recent woods of all kinds are easily made, but it requires con- 

 siderable dexterity to obtain them free of distortion, and of the necessary 

 tenuity. A little practice, however, will enable any person, who can guide 

 his hand steadily, to succeed to his satisfaction. When the slices are ob- 

 tained of the necessary thinness, they ought to be placed between two small 

 plates of glass, which are kept together by applying gum, sealing-wax, or 

 any adhesive substance round their edges. The best instrument is a broad 

 knife, thin in the back, with a straight and very sharp edge. 



In preparing fossil woods, the following directions may be of use. Let 

 a thin slice be cut off in the direction required, that is, transversely or lon- 

 gitudinally. It is to be ground flat, and then polished. The smooth sur- 

 face thus obtained is to be cemented to a piece of plate-glass, by means of 

 Canada balsam, of which a thin layer is to be applied to the slice of fossil 

 wood, and another to the glass. They are then placed on a plate of metal, 

 and gradually heated over a slow fire, so as to inspissate the balsam, care 

 being taken not to raise the heat so high as to produce air-bubbles in the 

 fluid. The slice and the glass are then removed, and placed upon each 

 other ; the superfluous part of the balsam being squeezed out by a slight 

 degree of pressure, accompanied with a sliding motion. When the prepa- 

 ration has cooled, the portion of balsam adhering to the edges of the slice is 

 to be removed with a pen knife, and the slice is ground down to the requi- 

 site degree of thinness, and polished. 



It is proper to add, that considerable labour and time must be em- 

 ployed in the grinding and polishing ; and those who may not be disposed 

 to apply much of either to a merely mechanical operation, may be supplied 

 with perfect specimens of all the plants figured in the present work, by Mr 

 Sanderson, Lapidary, St Andrew's Square, Edinburgh, who has brought 

 the art to great perfection. 



