Journal of Applied Microscopy. 389 



METHODS IN PLANT HISTOLOGY. 



Charles J. Chamberlain. 



IV. 



STAINING. 



Staining is one of the most important and most complicated processes of 

 microtechnique. The formulae are largely empirical and there is still abundant 

 room for experimentation in the use of mordants and in the effect of the same 

 stain or combination after various fixing agents. 



Stains may be classified in various ways ; e. g., there are three great groups 

 of stains — the Carmines, the Hematoxylins, and the Anilins. Stains may be 

 classified as basic and acid, or they may be regarded as general and specific. 

 A general stain affects all the elements, while a specific stain affects only certain 

 elements or stains some elements more deeply than others. Stains which show 

 a vigorous affinity for the nucleus have been called nuclear stains, and those 

 which affect the cytoplasm more than the nucleus have been termed plasma 

 stains. Of course, such stains are specific. 



We shall consider some of the more important haematoxylins, carmines, and 

 anilins, reserving general directions and theoretical questions for a subsequent 

 paper. Many of the formulae are taken from " The Microtomist's Vade-mecum " 

 (Lee), which is easily the most complete compendium of stains and other 

 reagents concerned in microtechnique. It is to be regretted that botanists have 

 no book of this character, but it must be confessed that we have not the material 

 for such an extensive work. Other formulae are from " Botanical Mici'otechnique" 

 (Zimmermann), and from " Stirling's Histology." The directions for using a 

 stain apply to stains made up according to the formulae which are given here 

 and may need modification if other formulae are employed. It is hoped, however, 

 that the directions will give the student sufficient insight into the rationale of 

 staining to enable him to make any necessary modifications. 



THE HAEMATOXYLINS. 



The most important haematoxylins are Delafield's hematoxylin, Kleinenberg's 

 haematoxylin, Erlich's haematoxylin, Boehmer's haematoxylin, Mayer's haem-alum, 

 and Haidenhain's iron-alum-haematoxylin. 



All the haematoxylins mentioned above contain alum, and according to Mayer, 

 who has written the most important work on haematoxylin stains (Ueber das 

 Farben mit Haematoxylin. Mitth. a. d. Zool. Station zu Neapel. 10: 170-186, 

 1891), " The active agent in them is a compound of haematin with alumina. 

 This salt is precipitated in the tissues, chiefly in the nuclei, by organic and 

 inorganic salts there present (e. g., by the phosphates) and perhaps also by other 

 organic bodies belonging to the tissues." These salts are fixed in the tissues by 

 the killing and fixing agent, and when the stain is applied a chemical combina- 

 tion results. Haematoxylins stain well after any of the fixing agents described in 

 the preceding paper, but they are most effective when used after the chromic 

 acid series of fixing agents. 



