66 Botanical Microtechnique 



iliat has had a co\er glass affixed with balsam or synthetic resin. 1 he 

 cover can be loosened and allowed to slide off by immersing in a jar 

 of xylene as long as necessary. After the cover has slid off, transfer the 

 slide to the absolute alcohol after the de-waxing xylene, run down to 

 water and proceed Avitli the restaining or destaining process. 



HEMALUM (REGRESSIVE) 



The destaining action of acids on hematoxylin is selective- 

 cytoplasm is destained more rapidly than cell walls, plastids, and 

 nuclear structures. This fact makes it possible to use a self-mordanting 

 hematoxylin as a stain that is adequately differential for many 

 subjects. The slides are purposely overstained in Delafield's, Harris', 

 or Mayer's hemalum, then destained in acid until the proper contrast 

 is obtained. 



The foregoing single stain, using a self-mordanting hematoxylin 

 formula, either as a progressive or regressive stain, deserves more 

 extensive use for routine diagnostic examination of research material. 

 An enormous amount of time and energy can be spent in ajjplying 

 elaborate multiple stains to large numbers of slides, many of which 

 are discarded after a moment's examination. In such a series of slides, 

 stained with a single stain, the few slides having the desired stage can 

 be easily restained if a more diagnostic differential stain is needed. 



HEMALUM WITH A "GENERAL" COUNTERSTAIN 



The foregoing hemalum stain can be supplemented by a counter- 

 stain, a stain that has little specific selectivity, but furnishes optical 

 contrast for the principal stain. A counterstain is introduced into the 

 staining series at a place having approximately the same water 

 concentration as the solvent of the counterstain. One of the most 

 useful counterstains is erythrosin. llie stock solution contains 1/2% 

 stain dissolved in 95'/( alcohol. Referring to Staining CJhart II, note 

 that the slide, previously stained to the correct intensity in hemalum, 

 rinsed and alkali/.ed, is put into erythrosin alter 95*^^ alcoliol. Ihe 

 interval in erythrosin nuisi be determined hv trial and may range 

 liom a few seconds to I In. This counterstain is remo\'ed from 

 different types ol material in variable degree by tlie siihsc (luent 

 dehydration. The final intensity ol ilu- pink counterstain depends on 

 ilic tcnacilN witli Avliidi ilic tissues retain tlic stain. 11 the ])ink color 

 is too dark, it will obscure some ol ilic details stained blue by the 

 hematoxylin. Excess counterstain can be removed by running the 

 slide back to 50',' alcohol. More pink can be added as sliowii on 



