358 
Journal of Agricultural Research voi. xxiii, no. 5 
not apparent in the previous studies As has been pointed out, the 
sudden break in the curve of percentage of water, which has held a 
steady trend from flowering, could come about only through the abrupt 
termination of growth. It is not evident from these or previous figures 
whether this abrupt termination involves the whole kernel at once or 
whether there has been a final abrupt termination of activity in a 
limited area preceded by a gradual abandonment of tissue to the point 
where the active tissue remaining affords an insufficient volume in which 
to take care of the starch produced daily by the plant. 
COLOR AS AN INDEX OF MATURITY 
Although the figures, taken by themselves, do not afford sufficient 
basis for the analysis of the final phases of maturation, the color formed 
in the Jet variety offers a suggestive clue. The melanin-like pigment 
is apparently deposited only when activity has ceased. In the normal 
kernel the color appears just before final maturity. The earliest traces 
are found about the twentieth or twenty-first day after flowering. If 
a kernel is removed from the spike even six days after flowering, the 
black color will appear on drying. It seems reasonable to suppose then 
that when this color appears on the kernel, the section of the kernel 
immediately beneath it has ceased to function. That this assumption 
is plausible is evidenced by two related observations. The black color 
appears first on the dorsal surface just below the tip. The tip of the 
kernel up to this time consists of active tissue remaining from the ovary 
walls. As soon as the black color appears, this tissue withers, showing 
that the vascular system here has ceased to function. This peculiarity 
has been noted in other years, when it had been found possible to measure 
the true length of the kernel only after the withering of the tip. Previous 
to that time the measurement necessarily had to include tissues which 
had no real connection with the growth inside the nucellus. It was also 
in this region that cells showing early abandonment as active reposi¬ 
tories for starch are most numerous, indicating that this region was the 
first to show lack of free movement of cell solutes. 
The progress of color formation and loss of water, as evidenced by the 
denting and collapse of the kernels, is very definite. Traces of color 
appeared when the moisture content was about 62 per cent. It was 
present on most kernels by the time they had reached 60 per cent. The 
spot was very definitely marked when they had reached 58 per cent, and 
the area had spread well toward the end of the kernel when the water 
content had reached 56 per cent. Denting appeared at about 55 per 
cent and was common at 51 to 52 per cent. Color appeared on the 
ventral surface of the grain at 53 per cent and was on the ventral surface 
of most kernels by the time they had reached 48 per cent. The sides 
as well as the dorsal surface had begun to dent at about 50 per cent and 
were commonly dented at 46 per cent. The ventral surface was black 
with the exception of the furrow on some kernels at 46 per cent and 
commonly so at 43 per cent. Even the furrow was black in some instances 
at 42 per cent. Few furrows with traces of green were found under 40 
per cent. Fine wrinkles appeared all over the kernel at percentages 
about 30 and on all kernels containing below 24 per cent of water. 
When these color observations are considered with the data previously 
presented, they assist materially in the interpretation. The black area 
on the dorsal surface became marked about the twenty-second day after 
