30 
Mycologia 
But having learned, through experience, that colors appear 
brighter when spread over large surfaces than when confined to 
smaller ones, it was decided to cover the spore-print entirely with 
a piece of white paper measuring 15.5 cm. by 29 cm., and provided 
in the center with an aperture of the exact size of the color 
squares ; a contrivance known as an excluder. Placing this ex- 
cluder over the print so that only a small patch of the spore- 
covered surface showed, and then comparing this patch with the 
squares, it was learned that the tone 13 m on PI. Ill matched 
perfectly, the reduction in area having had a darkening effect. 
For the next test, a piece of carbon paper of the same size as 
the white sheet was procured, and, after providing it with an 
aperture of the same dimensions as the other, comparison was 
made. This time the spores agreed exactly with square i, column 
13', pi. XV, a tone, it will be noticed, very much lighter than 
either of those determined upon in the foregoing tests. 
Finally, it was concluded to equalize conditions absolutely, both 
as to size of aperture and color of paper. Two sheets of the 
identical color of the mounts in Color Standards, cut to the size 
adopted for these tests, were applied, one to the print, the other 
to the squares, with the result that the spore-color tallied ac- 
curately with 13' k, on PL XV , — again a different tone. 
These tests may be repeated by anyone who will follow the 
methods described. Any color will answer the purpose, though 
a critical one, such as an indeterminate brown of medium depth, 
will exhibit the mutations more markedly. With excluders of a 
lively color the effect is quite surprising, as another set of tests 
with a sheet colored Cendre Green (PI. VI, 35 b) demonstrates. 
Except for the color, the sheet was in every respect like those 
used previously, but before applying it, an experiment was per- 
formed that again exhibited the effect of increased area on colors. 
It was found that when any part of the surface was brought in 
direct contact with the square of Cendre Green, the agreement 
was perfect; when, however, the surface was viewed as a whole, 
the color approximated rather closely Vanderpoel’s Green (PI. 
VI, 33 b), a yellower green than Cendre Green. 
With this sheet the following changes were produced in some 
squares chosen at random : 
