INTRODUCTIOX. 



19 



94. A solution of any of the above dj'es consisting of one 

 gram witli enough water to make one hundred cubic centimeters, 

 although too strong for most cases, is ver^- convenient, since it 

 can easilj- be diluted at will. From even ver^- 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 dee[), a part of the color can be removed by 

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

 (see above 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 Ihe fibres of the baik 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. Tl.e following method proposed by Rothrock ' 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 daj- in a dilute 



' Botanical Gazette, September, 1879. 



