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gives directions for the preparation of the carmine stain that bears his 

 name. 



I propose, therefore, to bring before your notice to-night two processes 

 only, viz., single staining in logwood, and double staining in carmine 

 and aniline green, and shall refer only to the staining of sections, the 

 methods being equally applicable to sections of stems, petioles, peduncles, 

 leaves, ovaries, &c. In every case I shall confine myself to facts, and 

 only describe methods that I have tried and proved to be successful. 



Before I begin the practical part of this demonstration, let us assume 

 that we have a piece of the stem of a plant, from which we wish to mount 

 some sections. The various processes which will have to be employed 

 before the section is ready to be put away in the cabinet may be con- 

 veniently grouped as follows : — 



1st. Cutting, which may be subdivided into three processes — 



(a) The preliminary preparation of the stem, hardening or softening, 

 as the case may be. 



(b) The process of imbedding in a suitable material, and 



(c) The cutting process. 



2nd. Staining, which may in like manner be sub-divided into two pro- 

 cesses — 



(a) Bleaching, and 



(b) Staining proper. 



3rd. Mounting, which may include also labelling. 



Whether we use logwood, carmine, or other stain, we must first pre- 

 pare the sections for receiving the stains by bleaching, except in the 

 few instances where they are already colourless. If, as in the present 

 instance, we wish to stain the formed material only, without having 

 regard to the cell-contents, either in order to render the outlines of the 

 cells, fibres, and vessels more distinct, or to differentiate them one from 

 the other, the only preparation I have found of any use is a solution of 

 chlorinated soda, which may be prepared as follows : — 



Dissolve 2oz. of powdered washing soda (hydrated sodium carbonate) 

 in half-a-pint of distilled water. Then shake up thoroughly loz. of 

 chloride of lime in a like quantity of distilled water ; add to this the 

 solution of soda, and again shake thoroughly. A precipitate of carbonate 

 of lime will be formed, the chlorinated soda remaining in solution. Allow 

 the precipitate to settle, pour off the clear solution, filter it, and preserve 

 it in a well-stoppered bottle in the dark. It is essential that the soda 

 should be slightly in excess, as, if the chloride of lime is not completely 

 neutralized, the lime that is left will combine with the carbonic acid of 

 the air during the process of bleaching, forming a film of chalk, which 

 will settle on the sections and completely ruin them. It will be best, 

 after the preparation is completed, to test a small quantity of the fluid 

 by adding to it some more solution of soda, when, if no precipitate is 

 formed, we may conclude that the chloride of lime is completely neu- 

 tralized. Should a precipitate, however, be formed, we must add more 

 solution of soda to the bleaching fluid, re-filter, again test, and, if necessary, 



