Jan. 15, 1925 
Ecological Relations of the Smut o f Maize 
163 
of the disease or the relation of growth 
factors to the organism (fig. 1). 
From the data published by Pammel 
and Stewart (IS), Hitchcock and 
Norton (8, Table 3), and Arthur and 
Stuart (2, Tables 49 to 52, inclusive), 
as well as from the studies made by 
the writers, it is evident that the lower 
nodal buds or rudimentary pistillate 
inflorescences (ears) (pi. 1, D), are the 
most common points of infection. 
The foregoing additional evidence of a 
tendency for more than one of these 
buds to become infected on the same 
culm emphasizes the possibility of a 
systemic development of the disease 
under field conditions, despite the 
repeated evidence of inoculation ex¬ 
periments and the commonly accepted 
belief that the infection is strictly 
local in its development. 
To begin with, the problem in¬ 
volves the possibility that if several 
sori appear on a plant they may have 
had a common origin. In this con¬ 
nection it should be recalled that only 
a comparatively short time, perhaps 
six to eight weeks, is required by the 
maize plant to develop from the stage 
in which the stem (morphologically 
speaking) is but a cone of tissue from 
1 to 2 inches in length and largely in 
a meristematic condition, to that in 
which the various parts of the mature 
plant are differentiated and the stem 
has attained virtually its full height. 
It need not be assumed, therefore, 
that because a plant showed several 
points of infection at the end of this 
period of rapid growth, these arose 
either from the growth of the parasitic 
hyphae from one point to another, or 
entirely from separate points of in¬ 
fection. It should be remembered 
that the incubation period for the smut 
organism in the field is generally 
6 to 14 days, depending on environ¬ 
mental conditions. Therefore, full de¬ 
velopment and maturity of the sori 
would cover quite as much time as 
that required by the plant in growing 
from 1 to 2 feet in height. If, indeed, 
there had been but one primary in¬ 
fection to produce the several smut 
galls, it would have occurred at a time 
when there was but a small cone of 
meristem to be infected. The hyphae 
would have to spread only a very 
short distance in order to accomplish 
an infection in parts destined to be 
widely separated in the mature plant. 
Brefeld has shown that corn smut 
may produce sori in any young tissue 
and that the organism does not spread 
from the point of infection. But 
neither do any of the admittedly 
systemic cereal smuts spread through 
the host tissues to any great extent. 
The distribution of the parasite in all 
such instances is brought about by 
the host itself when the culm or culms 
develop. The problem in the present 
instance, therefore, is to determine 
the reaction between the host and 
parasite, rather than the capacity 
of the parasite to penetrate the develop¬ 
ing tissues of the host. 
INFECTION STUDIES 
That the relation between the host 
and parasite under field conditions 
is not one of true systemic develop¬ 
ment of the disease has become con¬ 
vincingly evident from the data of 
Pammel and Stewart (15), Hitchcock 
and Norton (8), Arthur and Stuart 
(2), Piemeisel (16), and several others, 
all of whom confirm Brefeld’s original 
conclusions. The writers also have 
repeated extensively similar experi¬ 
ments with numerous variations based 
on the idea that Ustilago zeae might 
be found to resemble somewhat the 
head smut of sorghum, Sorosporium 
reilianum (Kuhn.) Me Alp. (17), which 
attacks both sorghum and maize (11, 
12 ). This species develops systemically 
in sorghum from an infection occurring 
later than the very early seedling stage. 
In this respect it resembles the “Trieb- 
infektion” of Ustilago violacea (Pers.) 
Fckl., as noted by Hecke (6). How¬ 
ever, all attempts thus far have failed 
to produce any evidence of systemic 
infection in corn smut. 
Similarly, efforts to protect seedlings 
and young corn plants from infection 
have not succeeded in altering the 
frequency or nature of infection of 
plants in the field. This work has 
involved both chemical and thermal 
disinfection methods for seed and soil, 
as well as attempts to protect young 
plants from infection by careful disin¬ 
fection of the seed, sterilizing the soil, 
and starting growth in the laboratory 
and in cloth-covered beds. Notes were 
taken on about 9,000 plants, including 
controls, at Manhattan, Kans., St. 
Paul, Minn., and Mitchell, Nebr. 
The lack of satisfactory methods for 
absolutely excluding infection and 
controlling other conditions, however, 
marred the conclusiveness of the nega¬ 
tive results obtained. Nevertheless, 
the data are in accord with the results 
of other investigators, in leading to 
the conclusion that true systematic 
infection is not involved. 
