66 Methods in Plant Histology 



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 erythro- 

 sin, the nuclei of the spermatozoa took the cyanin, while the nuclei 

 of ova preferred the erythrosin; hence he proposed the terms "cya- 

 nophilous" 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 hermaph- 

 rodite, 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 



