64 METHODS IN PLANT HISTOLOGY 



while cellulose walls are scarcely affected and the stain is easily washed 

 out. 



Iodine green. — Use a 1 per cent solution in 70 per cent alcohol. 

 Stain for an hour, rinse in 70 per cent alcohol, dehydrate in 95 per cent 

 alcohol and absolute alcohol, clear in xylol or clove oil, and mount in 

 balsam. If the stain washes out too rapidly and does not give sufficient 

 differentiation, stain longer, overnight or even 24 hours. 



Lignified structures stain green, but, after proper washing, cellulose 

 is scarcely affected. A bright green may be left in the chromosomes 

 after all the stain has been washed out from the spindle. 



Acid fuchsin, erythrosin, and eosin are good contrast stains for mi- 

 totic figures. Acid fuchsin or Delafield's haematoxylin are good for 

 cellulose walls. 



Light green (Licht Griin). — Light green is an acid stain, soluble in 

 water, alcohol, or clove oil. It stains quickly and forms a sharp con- 

 trast with safranin or phloxine. 



Stain in safranin and then, with little or no washing out, stain in a 

 weak alcoholic solution of acid green (about 0.2 g. in 100 c.c. of 95 per 

 cent alcohol). From 20 seconds to about 1 minute may be sufficient. 

 The green rapidly reduces the safranin, and consequently the staining 

 must not be too prolonged. A successful preparation should show red 

 chromosomes and green spindle. Lignified walls should be red, and 

 cellulose walls, green. 



Malachite green. — A 1-3 per cent aqueous solution is good for cellu- 

 lose walls. The stain contrasts well with Congo red. 



Methyl green. — A 1 per cent solution in water is good for staining 

 lignified structures. Lee recommends that the solution be acidulated 

 with acetic acid. This is not necessary for staining lignified membranes 

 nor for staining chromosomes. Methyl green has long been a favorite 

 stain for hving tissues. It is more easily controlled than iodine green, 

 especially in double staining to differentiate lignified and cellulose 

 walls. 



Acid green. — Make a solution according to the general formula, or 

 simply make a 1 per cent solution in water. This stains cellulose walls 

 and achromatic structures, but scarcely affects hgnified walls or 

 chromosomes. 



Anilin blue. — Strong alcoholic solutions are best for botanical work. 

 Even though the dry stain may be intended for aqueous solution, 

 make a 1 per cent solution in 85 or 95 per cent alcohol. 



