150 
METHODS IN PLANT HISTOLOGY 
one will be able to estimate the probable photographic result by 
making a visual examination with first one and then another of the 
filters in place. 
An example of how the filters were chosen in making one particular 
photomicrograph of a stem section may be suggestive. The specimen 
was well stained in safranin and anilin blue. If the photograph had 
been made on an ordinary uncorrected plate and without a filter the 
result would have been unsatisfactory. The red of the safranin 
would have taken as pure black while the parts of the specimen stained 
in anilin blue would hardly appear in the photograph because the 
plate was not sensitive to red and very much oversensitive to blue 
giving the blue almost the value of white light. Therefore we used 
a color-corrected plate and a combination of the Wratten “B” and 
“E” filters which gave the maximum contrast for the anilin blue since 
the spectral transmission band of the combination is entirely included 
within the limits of the absorption band of the anilin blue. While 
these filters did not give the maximum contrast for the safranin- 
stained portion of the specimen, the contrast was sufficient and the 
result was more satisfactory than if the safranin stain had photo¬ 
graphed as pure black because all detail in the vessel walls would 
then have been lost. 
A booklet, “Photomicrography,” published by the Eastman 
Kodak Company, includes a table showing the spectral absorption 
bands of some of the stains used in botanical microtechnic. It also 
gives data on the transmission spectra of the Wratten “M” filters. 
The Abbe condenser, which should not be used at all with low 
powers, is very useful with objectives of 8-mm. focus and all higher 
powers, especially if the condenser is achromatic. If the condenser 
is not achromatic, it is sometimes a good plan to remove it and 
in its place put a 16-mm. objective, or, for very high powers, even 
an 8-mm. objective. The condenser may be fastened into the con¬ 
denser sleeve by an improvised ring or collar. Zeiss makes a collar 
for this purpose. Spencer microscopes also have such collars. 
In addition to the Abbe condenser, there should be another, 
placed between the microscope and the light. For this purpose, 
the large condenser from a projection lantern may be used. For 
magnifications higher than 100 diameters still another condenser will 
be useful. Place it between the last-named condenser and the 
microscope. 
