520 
Journal of Agricultural Research 
Vol. XXIII, No, 7 
a poured agar plate. The numerous colonies appearing indicate the 
abundant internal spore production. 
Many samples of seed corn show slight discoloration of the seed coat 
near the germinal end. These discolorations become pronounced during 
germination and assume various colors such as pink, lavendar, or black. 
The black discolorations were found most consistently with Diplodia 
infection, the lavendar with Fusarium moniliforme , and the pink with 
Gibberella saubinetii . This condition we consider the result of the 
fungus progressing beyond the cavity and becoming established in the 
tissue comprising the pericarp. We have observed this condition in 
kernels before and during germination. This method of internal infec¬ 
tion explains the failure to secure disease-free seed by methods of disin¬ 
fection, The tissue of the cap, even with extensive presoaking, fails to 
soften materially. The long exposures to various disinfectants are not 
entirely effective even subsequent to presoaking. Such treatments 
usually injure the embryo and retard germination. 
Cross and longitudinal sections through the germ end of those inter¬ 
nally infected kernels show the mycelium also established in the tissue of 
the cap. In some cases the mycelium is observed among the thin-walled 
cells near the periphery of the cap. The mycelium is not abundantly 
established, but it is observed ramifying between as well as penetrating 
the cells. The thick-walled cells toward the vascular strands do not 
appear to be penetrated. In several instances long intercellular hyphae 
were observed in the vascular tissues. The development of the fungus in 
the cavity is probably subsequent to the infection of the tissue com¬ 
prising the cap. So far in our studies there was no conclusive evidence 
to show that such internal infection was always by means of the vascular 
system as the result of stalk or shank infection, 
GENERAL DISCUSSION 
With the nature of the internal infection determined, the means by 
which the fungus gains entrance and its relation to methods of control 
remain to be established. 
According to the occurrence of seed com infection, we must reckon 
with two means of infection quite independent of each other. 
First; Direct kernel or blossom infection. Silk as the path of infection 
has been considered a common method for Diplodia zeae by Heald, 
Wilcox, and Pool (16) and Van Der Bijl (38) and for Fusarium monili- 
forme by Valleau (36). No conclusive proof has been advanced to show 
that infection occurs by means of the stigma. It is considered, in view 
of the work so far reported, that such infection occurs because the silk 
stage offers an accessible means of entrance. The silk, becoming dry 
and shriveling when the com is in the late milk or dough stage, affords 
an opportunity for infection by wind-borne spores. Such type of infec¬ 
tion apparently accounts for the ears shown in Plate 13, A parallel 
type of infection appears to be the most common for wheat scab as 
reported by Adams (j). Moisture conditions in the cup before maturity 
of the ear are no doubt favorable for development of the fungi once they are 
established from external sources. This tissue of the cap offers little 
resistance to these parasites and would allow for their establishment and 
development into the cavity under the cap. The prevalence of infection 
under these conditions would depend upon exposures of ears in the field 
to favorable conditions for infection. The study of infected kernels 
failed to indicate whether infection resulted by this means or from vas- 
