508 SUMMAKY OF CUERENT RESEARCHES REIiATING TO 



Staining Sections. — Apart from the preparation of sections for ex-, 

 liibition purposes, staining should never be resorted to "without some 

 definite end in view. By subjecting tissues to the actions of stains the 

 tissues are more easily discerned and differentiated ; therefore we 

 should use the stain most suited to the purpose. Stains may be used 

 generally fo attack (1) the ground tissue ; (2) tbe nuclear structure. 

 The behaviour of various tissues in the presence of aqueous or alcoholic 

 solutions of the various dyes is of great advantage to the biologist. In 

 Botany, when an aqueous stain is used, both hard and soft structures 

 are stained, but the addition of an alcoholic stain of different colour has 

 the property of discharging the aqueous stain from the softer tissues, 

 while the af[ueous stain is still retained in the harder structure. The 

 following list of stains and their action on the various structures in 

 plants may be useful : — 

 Cellulose : — 



Iodine— yellow. 

 Iodine + HoSO^ — blue. 

 Chlor. zinc iodine — blue-violet. 

 Hfematoxylin — blue. 

 Carmin plus mordant— red. 

 It is also stained by meth. blue and other aniline dyes. 

 Lignified Cell-walls : — 



Iodine — strong yellow. 

 An. sulphate — bright yellow. 



Carbolic-hydrochloric acid — green (in presence of light). 

 Carmin and hematoxylin have no action, Ijut it is readily stained 

 by aniline colours. 



Corky or Cutiadarieed Walls : — 



Stain with aniline colours. 

 Carmin and htematox. — no action. 

 Cliitin : — 



(i) Meth. blue (acid), 

 (ii) Erythrosin. 

 With regard to the stains, the author generally made up his own 

 from the powder form, as they worked out much cheaper in the end by 

 this means. He had some really good and efficient stains made from the 

 old penny packets of aniline dyes, especially an aniline acid green made 

 some four years ago. The stains he generally employed were as follows : — 



. J Saffranin, aqueous. 



I Aniline green (acid), alcoholic. 

 -n J Carmin borax. 



I Acid an. green. 

 p I Fuchsin, aqueous. 



( Meth. green, alcoholic, 

 jx I Hgematoxylin, acid (Ehrlich). 



i Erythrosin, alcoholic. \ 



The sections should for preference be placed in a watch-glass, and 

 covered with a stain of an aqueous nature. They may be safely handled 

 with a camel-hair brush or section-lifter. To exclude dust, wine-glasses 



