162 
Journal oj Agricultural Research 
Vol. XXX, No. 2 
number of the smutted plants, while 
the other 40 per cent occurred on 15 
per cent of the smutted plants. 
This tendency of infection to de¬ 
velop at more than 
Fig. 1 . —Schematic drawing 
of mature culm of maize, 
showing only those struc¬ 
tures essential to an under¬ 
standing of the presence of 
meristematictissues. The 
apical “ bud ” bears several 
nodes with the staminate 
inflorescence at the tip. 
At about the fifth node 
down, the first lateral bud 
occurs, usually producing 
the pistillate inflorescence, 
or ear. Buds below this 
also may produce ears, de¬ 
pending on varietal char¬ 
acteristics and growth con¬ 
ditions. Toward the base 
of the plant the internodes 
are very short and buds 
beneath the ground level 
tend to develop into suck¬ 
ers, reproducing the struc¬ 
ture of the parent culm. 
The lower buds may be¬ 
come infected and are 
sometimes mistaken for 
diseased “brace” roots, 
which are not often actu¬ 
ally involved 
one point on the 
same plant has 
been noted in 
numerous other 
instances (pi. 1). 
In 1913 a series 
of observations 
in eastern Kansas 
and Nebraska 
(and also at one 
point in Illinois) 
showed over 25 
per cent of 581 
infected plants 
to be smutted at 
more than one 
node. In the 
neighborhood of 
Washington, D. 
C., nearly 20 per 
cent of 78 plants 
were thus af¬ 
fected. In a field 
at Newton,Kans., 
in 1914, a very 
dry season, 15 
per cent of the 
pla nts were in¬ 
fected and 36 per 
cent of the 95 
infected plants 
were smutted at 
more than one 
node. At Mc¬ 
Pherson, Kans., 
with scarcely 5 
per cent infec¬ 
tion, about one- 
third of the 
smutted plants 
were similarly 
affected. At La 
Fox, Ill., of 58 
smutted plants, 
23 showed in¬ 
fection at two 
or more nodes. 
Again, in 1915, 
out of 324 smut¬ 
ted plants ob¬ 
served at points 
in Kansas and 
Indiana, over 30 
per cent pro¬ 
duced galls at 
more than one 
node. In addition to these, many 
hundreds of plants have been examined 
in the experimental plantings at Man¬ 
hattan, Kans., with similar results. 
Such data seemed inconsistent with 
the apparently well established ideas 
that corn smut develops its sorus only 
at the point of host contact and that 
infection arises from the mere chance of 
contact between aerial conidia and host 
plant. The fact that isolated nodal- 
bud infections are not entirely charac¬ 
teristic perhaps is not so easily explained 
unless it be supposed that the disease, 
in part at least, is systemic in character, 
as Pammel and Stewart ( 15 ) doubtless 
believed. Studies by the authors were 
begun, therefore, with the idea of 
checking all possible explanations of the 
problem presented. 
THEORY OF SYSTEMIC INFECTION 
The published data on the nature of 
corn-smut infection do not show an 
entirely clear conception of the develop¬ 
ment and morphology of the corn 
plant with relation to the occurrence 
of susceptible meristematic tissue. 
As shown by. Brefeld ( 4 ), and more 
recently confirmed by Piemeisel ( 16 ), 
Pammel and Stewart ( 15 ) state that 
“the tendency to form smut boils 
increases in the lower nodes.” Hitch¬ 
cock and Norton ( 8 ) vaguely distin¬ 
guish between infection of “rudimen¬ 
tary ears” and “nodes” but offer no 
further explanation. The number of 
nodal infections recorded in their table 
suggests that, for the most part, they 
should have been classified as rudi¬ 
mentary ears, because smutting of the 
true node itself is almost as rare as 
smutting of the internode. Arthur and 
Stuart ( 3 ) also appear to have over¬ 
looked the essential point, namely, 
that a bud exists at each of the lower 
nodes of the plant from the ear node 
down to the crown where the inter¬ 
nodes become very short. Their divi¬ 
sion of the plant into “five aerial 
regions” is purely arbitrary. They 
illustrate (pi. 10, A) and record in 
Tables 49 to 52 the exceedingly 
common infection of these nodal buds 
as infections of the stalk or stem. 
MacMillan ( 13 ) apparently attributes 
the axillary infection to the presence of 
moisture in the sheaths rather than to 
the presence of meristem at the node. 
MORPHOLOGY OF THE HOST 
Because of the confusion which exists 
concerning the relation of smut in¬ 
fection to the structure of the corn 
plant, it seemed essential to clarify the 
conception of the morphology of the 
maize plant before attempting to 
analyze the problems of the etiology 
