1 82 BOTANICAL MICROTECHNIQUE. 



placing objects stained with haematoxylin for a short time 

 in a \% solution of potassium bichromate or a concentrated 

 aqueous solution of picric acid. Both fluids must, of course, 

 be carefully washed out before the transfer to Canada bal- 

 sam or glycerine-gelatine. 



317. In dealing with objects to be sectioned with the 

 microtome, very pure nuclear stains may usually be obtained 

 by staining the objects in toto ("staining in mass") before 

 imbedding in paraffine. Since haematoxylin cannot pene- 

 trate the cuticle and therefore only penetrates from cut 

 surfaces, very different depths of staining are obtained, and, 

 at some distance from the original surface, only a nuclear 

 stain. Large objects must sometimes be left in the staining 

 fluid, which in this case should be used pretty dilute, for 

 -some time (often several days), in order to be sufficiently 

 stained. Very good mass-staining may be obtained by first , 

 staining large pieces of tissue deeply with haematoxylin and 

 then placing them for a considerable time in a \<f> solution of 

 potassium bichromate. 



ft. Carmine. 



318. Only a few of the numberless different carmine 

 solutions can be described in detail here. These, as well as 

 various other staining media containing carmine, can be 

 obtained ready for use from chemists. 



1. Grenadier s borax-carmine can be prepared by dissolv- 

 ing 4 grams of borax and 2 to 3 grams of carmine in 93 ccm. 

 of water, then adding 100 ccm. of 70$ alcohol, shaking and 

 filtering. This solution is used for staining in mass as well 

 as for sections. For washing, acid alcohol and a solution of 

 borax or oxalic acid in spirit are recommended. 



2. Beale's Carmine. .6 gram of carmine is shaken up with 

 3-75 grams of liquor ammonii caust. [aqua ammoniae, U. S. P.], 

 then boiled for a few minutes ; after an hour, 60 grams of 

 glycerine, 60 grams of water, and 15 grams of alcohol are 

 added, and the whole is finally filtered. 



3. Ammonium carminate is best prepared by dissolving in 

 \vater to which a little (about .5$) ammonium carbonate has 



