70 
METHODS IN PLANT HISTOLOGY 
green would be a poor combination, for both would stain chromo¬ 
somes and neither would stain the spindle; both would stain lignified 
structures and neither would give satisfactory results with cellulose 
walls. Both stains are basic. Acid green would have given a con¬ 
trast in both these cases, because it stains achromatic structures and 
cellulose walls. In general, an acid stain should be combined with 
a basic one, but there are so many exceptions that it is hardly 
worth while to learn a list of basic and acid stains. Stains which 
stain chromosomes are likely to be basic, and those which do not stain 
chromosomes are likely to be acid or neutral. If it were true that 
acid stains affect only basic structures, and basic stains affect only 
acid structures, a classification of stains would be of great value. 
Safranin and gentian-violet are both basic, but with proper washing 
out the chromosomes are red and the spindle is violet, the safranin 
being washed out from the spindle, while the gentian-violet is washed 
out from the chromosomes. The only way to insure success is to 
become familiar with the action of each stain upon the various 
structures. 
THEORIES OF STAINING 
In 1890 Auerbach, a zoologist, published the results of his studies 
upon spermatozoa and ova. He found that, if preparations contain¬ 
ing both spermatozoa and ova were stained with cyanin and erythrosin, 
the nuclei of the spermatozoa took the cyanin, while the nuclei of 
ova preferred the erythrosin; hence he proposed the terms “cyano- 
philous” and “erythrophilous.” Auerbach regarded these differ¬ 
ences as an indication of sexual differences in the cells. 
Rosen (1892) supported this theory, and even went so far as to 
regard the tube nucleus of the pollen grain as female, on account of its 
erythrophilous staining. In connection with this theory it was 
suggested that the ordinary vegetative nuclei are hermaphrodite, 
and that in the formation of a female germ nucleus the male elements 
are extruded, leaving only the erythrophilous female elements; 
and, similarly, in the formation of a male nucleus the female 
elements are extruded, leaving only the cyanophilous male elements. 
As long ago as 1884 Strasburger discovered that with a mixture 
of fuchsin and iodine green the generative nucleus of a pollen grain 
stains green, while the tube nucleus stains red. In 1892, in his 
Verhalten des Pollens, he discussed quite thoroughly the staining 
reactions of the nuclei. The nuclei of the small prothallial cells of 
