THE WILT DISEASE OF PIGEON-PEA. 23 
seed originated, showed, however, that the disease was not known 
there. Its field characters were similar in many respects to those 
of the wilts described above, and perithecia of Neocosmospora 
vasinfecta were found to be common on the roots of diseased 
plants. What connection, if any, exists between the introduction of 
the new species of plant and the outbreak of disease is not clear, but 
it appears possible that a parasite already present on some other 
crop found the new species susceptible to attack and through it 
passed to the species common in the district. The interesting 
conception of “‘ bridging species’’ already established for the host 
plants of the Erysiphacez and rusts may be called into account 
for the appearance of wilt in indigo. Both the species of indigo, 
Indigofera sumatrana and I. arrecta, were attacked, but the disease 
was most severe in the latter. 
Inoculation experiments were undertaken with Neocosmospora 
vasintecta from indigo, cotton, gram and pigeon-pea. 
SERIES XII. 
(a) Indigo inoculated with Neocosmospora vasinfecta from indigo. 
The culture used was obtained as described under Series X 
from the root of a wilted plant of Indigofera sumatrana, and bore 
numerous perithecia. 
The plants were grown in pots, the pots and soil being unsteril- 
ised. The seed of the Sumatra variety was untreated in any way, 
while that of the Java variety was steeped for 20 mimutes in strong 
sulphuric acid to promote germination, since it belongs to the cate- 
gory of ‘‘hard seeds’’ requiring treatment to rupture or soften the 
seed coat before sowing. 
The inoculations were made by sprinkling the seed and soil 
after sowing but before covering, with the culture broken up im dis- 
tilled water. 
A second series was made, using a culture derived from a wilted 
plant of Indigofera arrecta. 
