Journal of Applied Microscopy. 437 



METHODS IN PLANT HISTOLOGY. 



Charles J. Chamberlain. 



V. 



GENERAL REMARKS ON STAINING. 



Many things may be examined alive without kilUng, fixing, staining, or any 

 of those processes. A filament of Spirogyra shows the chromatophore nicely if 

 merely mounted in a drop of water ; the nucleus may be visible, and the 

 pyrenoids can usually be located. Of course, such a study is necessary if one is 

 to understand anything about the plant, and in an elementary class this might 

 be sufficient, but a drop of iodine solution applied to the edge of the cover would 

 emphasize certain details, e. g., the starch in the pyrenoids would appear blue, 

 the nucleus a light brown, and the cytoplasm a lighter brown. This illustrates 

 at least one advantage to be gained by staining ; it enables us to see structures 

 which would otherwise be invisible, or almost invisible. 



With so many stains at our disposal, it at once becomes a problem just 

 which stain or combination to use in each particular case. Beautiful and 

 instructive preparations occasionally result from some happy chance, but uniform 

 success demands skill and judgment in manipulation, and also a knowledge of 

 the structures which are to be differentiated. Let us take a vascular bundle for 

 illustration. Safranin stains the xylem a bright red, but, with judicious washing, 

 is entirely removed from the cambium and cellulose elements of the phloem. A 

 careful staining with Delafield's haematoxylin now gives a rich purple color to 

 the cellulose elements which were left unstained by the safranin, thus contrasting 

 sharply with the lignified elements. If cyanin and erythrosin be used, the 

 xylem takes the blue and the cambium and phloem take the red. Many terms 

 have been given to indicate the affinity of certain tissues for certain stains. 

 Auerbach used the terms erythrophilous and cyanophilous in 1890. This emi- 

 nent zoologist studied spermatozoa and ova. He found that if preparations 

 containing both spermatozoa and ova were stained with cyanin and erythrosin, 

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

 preferred the erythrosin ; hence the terms cyanophilous and erythrophilous. 

 Auerbach regarded these differences, 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 {Verhalten des Pollens), \\e. discussed quite 



