CHAPTER IV 
GENERAL REMARKS ON STAINING 
Many things may be examined alive without killing, 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 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. Much of the recent progress in morphology and cytology 
has been due to the development of critical methods of staining. 
Some of the combinations and methods recommended by various 
workers are good in themselves, while others, not so good, have 
yielded results because they have been so skilfully used. 
SELECTION OF A STAIN 
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 while the 
cambium and phloem take the red. 
The mere selection of two colors which contrast well is not 
sufficient. Green and red contrast well, but safranin and iodine 
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