AND HOW TO USE IT. 101 



fluid, carbolic acid water, very dilute spirit and water, and even 

 distilled water, will preserve some vegetable tissues for a great 

 length of time. The pith from the stem of various plants, the 

 epidermis, and many other vegetable tissues may be preserved as 

 dry objects very satisfactorily. 



Preparation of Vegetable Sections. — Not only do we find, as 

 a rule, that the texture of many vegetables is of too great density 

 to be readily cut in the natural condition, but they also contain 

 much resinous and other matter, of which it is highly desirable to 

 get rid. Let us take a stem or root, and first cut it into short 

 lengths, which are to be placed in water for three or four days, by 

 which time all the soluble, gummy matters will have disappeared. 

 The pieces are now transferred to a v/ide-necked bottle, containing 

 methylated spirit, which, in the course of a few days, will dissolve 

 out all the resin, etc. Many kinds of woody tissues are by these 

 processes reduced to a fit condition for immediate cutting. Others, 

 however, are so hard as to render it necessary to give them ano- 

 ther soaking for some hours in water, to bring them to a sufficient 

 degree of softness to cut easily. If the wood (as will happen 

 sometimes) be still too hard for cutting sections, a short immer- 

 sion in warm, or, if necessary, boiling water, will not fail effect- 

 ually to soften it. 



Unprepared Vegetable Tissues. — Special directions are given 

 in text-books on the subject. For instance, it is recommen- 

 ded to lay the leaf, etc., on a piece of fine cork, and with a 

 sharp knife to shave oft' thin slices, cutting down upon the cork, 

 etc. No method, however, is at once so simple and successful as 

 the process of imbedding in paraffin. To do this, it is necessary 

 to make a paper mould, by twisting a strip of stout writing-paper 

 round a thin ruler, and turning in the paper over the end of the 

 ruler. This mould, the height of which may vary from an inch to 

 an inch and a-half, should now be half filled with melted paraffin- 

 mixture, which is made by mixing paraffin with one-fifth its weight 

 of common, unsalted lard, a gentle heat applied, and the two sub- 

 stances thoroughly stirred together; the leaf or other object 

 plunged into it, and held in position by forceps till the paraffin has 

 become sufticiently solidified to yield it a support. Take care that 



