256 
Journal of Agricultural Research 
Vol. I, No. 3 
or only rarely so. (PI. XXIII, fig. A.) They are irregular in form and 
vary greatly in size, averaging about 300/1 through their greatest diam¬ 
eter. 
In cross section the pycnidia from the stem and roots show somewhat 
different structures. From either source they are completely inclosed 
by a dark, almost black, outer wall (PL XXV, A and B). 
The pycnidia on the roots have a well-defined inner hyaline layer 
almost equal in thickness to the outer wall (PI. XXV, A). On the stem 
the dark wall is more conspicuous, being better developed than on the 
root, and the inner hyaline layer is completely lacking (PI. XXV, B). 
The basidia are short, fragile, somewhat inconspicuous, and arise from 
the inner hyaline layer or from the dark wall in pycnidia where the hya¬ 
line layer is absent. They are 6 to 13/* in length and very narrow. 
The spores are discharged through a beak varying somewhat in length, 
which may arise from any part of the upper surface of the pycnidium. 
In old dried specimens the upper portion of the pycnidium may fall 
away. 
Pycnospores. —The pycnospores are oblong, rounded at both ends, 
6.8 to io.o ( u long by 3.4 to 4.1 p. wide, with two large oil droplets. They 
are hyaline, 1-celled, and sometimes slightly curved (PI. XXV, F ). 
In the same pycnidium on the host and occasionally on rice and on 
sweet-potato-stem cultures are found in addition to the pycnospores hya¬ 
line curved or straight bodies 6 to 15 pi in length. These bodies are 
somewhat cylindrical in shape and rounded or tapering at the ends (PI. 
XXV, G). The function of these bodies is not known. Several attempts 
have been made to germinate them, and while there have been some rea¬ 
sons to believe that a germ tube was developed, this point was not defi¬ 
nitely settled. These bodies were formed so sparingly in artificial media 
that it was necessary to use those from the host in order to test their 
germination in hanging-drop cultures in Van Tieghem cells. Because 
of the difficulty in sterilizing this material, bacteria completely overran 
the cultures in about 24 hours, thus terminating the experiment. 
PARASITISM OF THE ORGANISM 
INOCULATION EXPERIMENTS 
The details of inoculations with Plenodomus are found in the following 
pages. For convenience, the experiments are numbered and arranged 
according to dates of inoculation and under the heading to which they 
belong. The organisms used to make the inoculations are also desig¬ 
nated by numbers. 1 
1 For convenience and ready reference, separate numbers (100, ioi, 102, 108, and no) were given to the 
different isolations where they or subcultures from them were used for inoculations. No. 100 was 
given the organism obtained from specimens sent the writer Aug. 9, 1912, and No. 101 from specimens 
collected Aug. 22 from the same locality. The other numbers used, 102, 108, and no, were given to the 
organism reisolated from inoculated plants. A new number was given the fungus only when it was the 
source from which other plants were to be inoculated. However, it should be kept in mind that these 
different numbers represent only different isolations of the same organism (Plenodomus destruens). 
