THE WILT DISEASE OF PIGEON-PEA. 29 
formed singly when within the vessels, but in culture, or at the sur- 
face of the root in moist air, several are successively produced 
and remain bound together into a head by a watery or slightly 
viscid exudation from the tip of the sporophore. They thus 
belong to the form-genus Cephalosporium. On the surface of 
diseased roots and the base of the stem, beds of macroconidia of 
the type characteristic of the form-genus Fusarium are found. 
Fusarium spores, produced in this case singly, may also be derived 
from cultures of the microconidia, whether from within the vessels 
or from the bark. 
On the dead roots, especially after incubation in a moist 
atmosphere, perithecia of Neocosmospora vasinfecta can frequently 
be found. From the ascospores of these, micro- and macroconidia, 
indistinguishable from those just mentioned, can be obtained by 
cultivation. In some cases wilted pigeon-pea stems also bear 
perithecia of a Nectria, which again has micro- and macroconidia 
similar to the above. The indigo disease is in some respects (which 
need not be entered on here) somewhat unlike the others. Here 
also, however, the morbid anatomy is similar, and the same micro- 
and macroconidia and perithecia of Neocosmospora are common. 
The experiments described above resulted in not a single case 
of wilt being developed in cotton, indigo or gram when inoculated 
with cultures originatmg from the ascospores of Neocosmospora 
vasinfecta, whether from the same host or from any of the other 
three. In pigeon-pea apparent infections resulted in some cases, 
but these can all be accounted for by accidental inoculation from 
some other source and were not obtained when sterilisation of all 
the material used was rigidly carried out. The pigeon-pea wilt is 
very prevalent both on the Pusa Farm and in the surrounding neigh- 
bourhood, and sources of external infection are numerous and diffi- 
cult to exclude. On the other hand, the cotton wilt has not been 
observed in this district and the danger of external contamination 
is negligible. Indigo wilt has occurred on the Farm, but there was 
little of it either on the Farm or near by, and the same applies to gram 
