UNITED STATES DEPARTMENT OF AGRICULTURE 
Washington, D. C. T May 21, 1923 
INFLUENCE OF SPACING ON PRODUCTIVITY IN SINGLE-EAR AND PROLIFIC 
TYPES OF CORN. 
By E. B. Brown, Agronomist, and H. S. Garrison, Assistant Agronomist, Office of 
Cereal Investigations, Bureau of Plant Industry. 
CONTENTS. 
Page. Page. 
Single-ear and prolific types of corn 1 j Results of the experiments 5 
Location and plan of the experiments 4 Analysis of the yields 8 
Description of the varieties 5 i Conclusions 10 
SINGLE-EAR AND PROLIFIC TYPES OF CORN. 
Throughout the southern portion of the United States both the 
single-ear and prolific types of corn are more or less commonly grown. 
The distinguishing characters of the single-ear type are the usual pro- 
duction of but one well-developed ear per stalk (Figs. 1 and 2), large 
ears with numerous rows of kernels, and large cobs (Fig. 3). Under 
very favorable conditions two well-developed ears may be produced, 
but ordinarily secondary ears are stubby in appearance and classed 
as nubbins. In no variety, so far as known, is there a complete inhi- 
bition of secondary ears. As contrasted with the single-ear type, 
the prolific is distinguished by the normal production of more than 
one ear per stalk (Figs. 4 and 5). The ears usually are smaller and 
more slender, with fewer rows of kernels and smaller cobs (Fig. 6). 
The demarcation between the two types is not absolute. Between 
the two extremes varieties occur that are more or less intermediate 
and that can not be placed accurately in either class. In each type 
there are occasional plants that vary toward the opposite type. By 
the selection of seed from such individuals it would be possible to 
segregate a prolific strain from the single-ear type or a single-ear 
strain from the prolific. 
It is reasonable to assume that the development of the single-ear 
type has resulted from a more or less continuous selection toward a 
large ear. With this there has developed a tendency toward a high 
number of rows of kernels, large cobs, the suppression of extra shoots, 
and the development of but one ear per stalk. In the development 
of the prolific type the characters that have been perpetuated and 
intensified are the production of more than one ear per stalk and of 
small slender ears with usually a low number of rows of kernels and 
small cobs. It seems probable that in the single-ear type the char- 
35697— 23— Bull. 1157 
