238 Wisconsin Academy of Sciences, Arts, and Letters. 
tannin, insoluble in alcohol; “2-X”, described as similar in its 
reactions to except that it is soluble both in water and in 
alcohol; and “3-X”, described as the ‘‘coloring matter of the 
bark^’ . . . which “is estimated as tannin in bark analysis,” 
but “its real nature is unknown.” Extracts “1-X” and “2-X” 
were less toxic than “commercial” tannin while “3-X”, the 
coloring matter, was very toxic. They point out further a state¬ 
ment from Kerr to the effect that “chestnut trees of northern 
growth, say on a line north of the southern boundary of Pennsyl¬ 
vania, contain very materially less coloring matter than the growth 
south of it, and, as we all know, the wood in the latitude referred 
to seems to have been more susceptible than that further south.” 
The importance of the coloring matter as an inhibitive substance is 
thus suggested in this instance. Promme and Wingard (31) in a 
study of varietal susceptibility of beans to rust (Uromyces appen- 
diculatus (Pers.) Lev.) found that all varieties with solid red or 
red mottled seed were resistant, while those with white seed as 
a class were more susceptible than those of any other color. In the 
case of onion smudge (Colletotrichum circinans (Berk.) Vogl.), a 
bulb rot. Walker (84, 85, 86) has shown a very strict correlation 
between scale pigments and resistance. The white varieties are 
uniformly susceptible while the red and yellow varieties are only 
slightly attacked. The resistant principle can be secured by 
making a cold water extract of the dry, outer colored scale. This so¬ 
lution is highly toxic to the spores and mycelium of the fungus. A 
similar extract from white scales promotes normal germination 
and growth. When the dry outer scale is removed even colored 
bulbs are readily infected. The interpretation of this is found 
in the fact that the toxic substance is readily dissolved from the 
dead outer scales into the soil water thus deactivating the fungus 
before invasion. In the succulent scale the epidermal cells which 
are the ones containing the pigment show reduction of this pig¬ 
ment while the mycelium is still in the outer cell wall and has not 
actually invaded the cell lumen. This is due either to autolytic 
processes within the cell or to a diffusible substance secreted by 
the fungus. Resistance by the host, however, is accomplished by 
the dry outer scales which serve as a barrier to the fungus through 
the action of their soluble toxic substance. 
