Corn Investigations 
29 
BROAD FERTILIZATION IN CORN THE RULE 
RELATION OF SILKING AND POLLINATION 
Knowledge that inbreeding of corn is injurious has caused 
considerable speculation relative to the amount of inbreeding 
that actually occurs in the open field pollination of corn. 
For the purpose of determining the opportunity for cross- 
fertilization, the natural silking and tasseling relationships were 
studied during 1914 and 1915 for fourteen varieties. The varie- 
ties under comparison were grown at the normal rate of plant- 
ing (three per hill) in adjacent three-row plats of sixteen rods 
length. One hundred and twenty consecutive plants were 
tagged and numbered in each plat just before the blooming 
period. With the initial advent of tassels and silks, individual 
plant records were kept of their daily development. The cor- 
relations between the shedding of pollen and the pollination of 
silks and, indirectly, the fertilization of the ovules, are pre- 
sented in Tables 6 to 8 and summarized in Table 9. Data bear- 
ing upon the same relationships were obtained on a smaller 
scale with nine varieties in 1920 and are included in the sum- 
mary table. 
The upper portion of the central tassel spike is commonly 
the seat of the initial shedding of pollen. From here it extends 
downward and laterally to the tassel branches. The shedding of 
pollen begins with elongation of the anther filament and the 
extrusion and dehiscence of the anthers. Receptive silks are 
subject to self-fertilization as long as the plant bearing them 
sheds pollen. The exact time at which the pollen falls upon the 
silk which fertilizes the kernel is not directly apparent. This 
time can be approximated by noting the date upon which the 
characteristic slight discoloration and withering of the silk con- 
sequent upon fertilization is first apparent. 
In 1921 the time of discoloration and withering of the silks, 
which is evidence of fertilization having been effected, ranged 
from 42 to 72 hours after the pollen had been applied to the 
silks. For this determination the ears of 100 plants were cov- 
ered with paper bags before the silks appeared. Upon removal 
of the bags following silking, pollen was artificially applied and 
the time determined for each plant to show the effects. The 
data are given in Table 10. 
Varieties as well as individual plants were found to vary 
somewhat in the sequence of the various flowering stages of 
tassel and silk. With all varieties, however, as an average for 
the two years and with most individual plants, it appears that 
