CHAPTER III 



STAINS AND STAINING 



As edition after edition of this book has appeared, there has been a 

 decrease rather than an increase in the number of stains in general use; 

 but there has been a notable improvement in the use of some stains 

 which have long been popular. For cytological work Haidenhain's 

 iron-haematoxylin holds more firmly than ever its 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 haema- 

 toxylin to first place for cellulose tissues is no longer undisputed, for 

 anilin blue is giving excellent results and Hght green seems to give 

 more accurate views of the phloem than we were securing with any of 

 the other stains. However, it must be admitted that preparations of 

 coniferous woods, stained in safranin and Delafield's haematoxylin by 

 Thomson and his students at the Toronto laboratory, have not been 

 surpassed. 



The fact that excellent preparations can be made, almost without 

 trial, by using combinations already perfected doubtless deters in- 

 vestigators from experimenting with other stains. There is still abun- 

 dant room for experimenting with various stains, especially in the use 

 of mordants and in the effect of the same stain or combination after 

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

 microtechnique have so little knowledge of chemistry, and that chem- 

 ists have no interest in developing methods of staining. During the 

 past few years, American stains have been developed until many equal 

 and some even surpass the famous Griibler products; and, besides, the 

 American stains are becoming standardized. The Commission on 

 Standardization of Biological Stains, and especially its able president, 

 Dr. H. J. Conn, cannot be too highly commended for the great improve- 

 ment in American stains. The first standardized stain, methylene blue, 

 was put on the market in the summer of 1923 and, before the end of 

 the year, safranin was added. By the end of 1929, forty-three stains 

 had been certified. The certification means that the stain has passed 



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