CHAPTER III 

 STAINS AND STAINING 



During the past ten years no new stains of the first rank have 

 come into favor, but much greater precision has been attained in the 

 use of some which were already popular. For cytological work 

 Haidenhain's iron-haematoxylin holds a firm place at the head of the 

 list, with Flemming's triple stain an easy second. For anatomical 

 work, safranin still holds first place for the lignified elements of the 

 vascular system, but the claim of Delafield's haematoxylin to first 

 place for cellulose tissues is no longer undisputed, for anilin blue 

 is giving excellent results and light green (Licht Grun, as it reads 

 on the label) seems to give more accurate views of the phloem 

 than we were securing with any of the other stains. The fact that 

 excellent preparations can be made, almost without trial, by using 

 combinations already perfected doubtless deters investigators from 

 experimenting with other stains. There is still abundant room for 

 experimenting with various stains, and especially in the use of mor- 

 dants and in the effect of the same stain or combination after various 

 fixing agents. It is to be regretted that botanists who need micro- 

 technic have so little knowledge of chemistry, and that chemists 

 have no interest in developing methods of staining. 



Stains may be classified in various ways: e.g., there are three 

 great groups of stains the carmines, the haematoxylins, 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 ele- 

 ments, 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 



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