42 
METHODS IN PLANT HISTOLOGY 
We shall consider some of the more important haematoxylins, 
carmines, and anilins, reserving general directions and theoretical 
questions for another chapter. The formulas are largely empirical. 
Some of those given here are taken from The MicrotomisVs Vade- 
Mecum (Lee), which is easily the most complete compendium of 
stains and other reagents concerned in microtechnic. It is to be 
regretted that botanists have no book of this character, but it must 
be confessed that we have not the material for such an extensive 
work. Other formulas are from Botanical Microtechnique (Zimmer- 
mann) and from Stirling’s Histology , and still others are from current 
literature and from our own laboratory. The directions for using a 
stain apply to stains made up according to the formulas which are 
given here, and may need modification if other formulas are employed. 
It is hoped, however, that the directions will give the student sufficient 
insight into the rationale of staining to enable him to make any 
necessary modifications. Since American stains have come into 
general use, the need for rationale is even greater, especially if the 
American stains are made up according to standard formulas, which 
are based largely upon the Griibler products. In general, it would 
seem that the American stains are purer and that they act more 
rapidly. 
The current practice in staining paraffin sections on the slide 
differs from the practice in staining freehand sections or small objects 
which are to be mounted whole. In case of paraffin sections, the 
cell contents are usually as important and often more important 
than the cell walls; consequently, extreme care must be given to every 
detail. With freehand sections the cell contents often drop out, 
but even when they remain, the cell walls are usually the important 
features; and so the process is considerably shortened. 
For staining freehand sections, it is customary to use solid watch 
glasses, unless the sections are very large. The details of the method 
are given in chapter vi, on “Freehand Sections.” 
For staining sections on the slide, nothing is better than the 
ordinary Stender dish. The arrangement of Stender dishes shown 
in Figure 16 is very convenient. The advantage is obvious. With 
two dishes each of xylol, xylol-alchol, and absolute alcohol, one 
set can be used in passing down to the stain, and the other, which 
is thus kept free from any paraffin in solution, can be used in passing 
back to the balsam. Even for paraffin sections, some use only 
