INTRODUCTION. 



19 



94. A solution of any of the above dyes consisting of one 

 gram with enough water to make one hundred cubic centimeters, 

 although too strong for most cases, is very convenient, since it 

 can easily be diluted at will. From even very dilute solutions 

 parts of a specimen, for instance, a cross-section of a stem, will 

 take up some of the color with more or less change. If the 

 staining is too deep, a part of the color can be removed by 

 careful washing in alcohol, or in a very dilute acid or alkali 

 (see aliove table for each case). 



95. Double-staining. It is sometimes possible to color dif- 

 ferent parts of a specimen with more than one dye ; for instance, 

 staining the fibres of the bark green, and the wood of the same 

 specimen red. The best results are obtained by the use of an 

 alcoholic solution of one of the dyes and an aqueous solution of 

 the other. The following method proposed by Rothrock 1 gives 

 excellent results. The dyes are Woodward's carmin (see 88) 

 and anilin green (or '" iodine green"). The specimen (whether 

 bleached by sodic hypochlorite or left unbleached) is first 

 thoroughly saturated by alcohol, which hardens it, and causes 

 contraction of the contents ; it is then kept for a day in a dilute 



1 Jiotanical Gazette, September, X879. 



