BOTANICAL MICROTECHNIQUE. 



ccm. of /o^ alcohol with or without heat, the whole is 

 allowed to stand and then filtered. Washing with acid 

 .alcohol is usually unnecessary, but a weak solution of alu- 

 jninium chloride in alcohol, or alcohol containing 2\% of 

 glacial acetic acid, is sufficient for all cases. 



According to P. Mayer's statements, only Grenadier's 

 borax-carmine, of the numberless solutions heretofore rec- 

 ommended, presents any advantages over carmalum and 

 paracarmine. 



A. Meyer (V) recommends especially for staining the 

 niuclei of pollen-grains: 



10. Chloral Carmine. This is prepared by heating for 30 

 minutes on the water-bath .5 gram of carmine, 20 ccm. of 

 alcohol, and 30 drops of officinal hydrochloric acid,* and 

 then adding 25 grams of chloral hydrate. After cooling, the 

 .solution is filtered. It stains the nuclei of pollen-grains 

 deep red in ten minutes. In many cases I have obtained 

 ;good nuclear stains with this medium by washing the sec- 

 tions in boiling water on removing them from it. Such 

 preparations may be mounted in glycerine or may be trans- 

 ferred in the usual way to Canada balsam. 



[u. Czokors Alum cochineal has proved so good as a 

 nuclear stain for many vegetable tissues that it should have 

 a place here. It is prepared as follows : 7 grams of crude 

 pulverized cochineal (the dried insects) is boiled in a solu- 

 tion of 7 grams of burnt alum in 700 ccm. of water until the 

 whole is reduced to 400 ccm. The solution is then carefully 

 filtered and a few crystals of carbolic acid (phenol) are 

 added as a preservative.] 



319. All these solutions of carmine are adapted as well 

 for staining in mass as for staining sections. But they gen- 

 erally penetrate pretty slowly and require to act for a rather 

 long time. They are inferior in the sharpness of their stain- 

 ing to many other dyes, in most cases ; but usually give a 

 very purely nuclear stain. The cell-wall is especially seldom 

 stained by carmine. 



[* This has a specific gravity of 1.13 or 17 B.] 



