978 
Journal of Agricultural Research 
Vol. XXXI, No. 10 
data. This irregularity may be partly attributable to difficulty of 
chemical determination. 
Crude fiber and aluminum are unique in that they are the only 
constituents of the stalk, as determined, that do not undergo more or 
less marked depletion in the stalk coincident with the development 
of the seed. This suggests that the two are in some way associated. 
It is found from the equations given that K is the same in both cases, 
but that U falls 18.5 days later in the aluminum curve than it does in 
the crude-fiber curve. If the aluminum curve is shifted 18.5 days 
to the left, and superimposed on the crude fiber curve, the two curves 
coincide. Aluminum is thus directly proportional to the crude fiber 
of 18.5 days preceding. If aluminum is an essential element in the 
.building up of the crude-fiber tissues, its accumulation should occur 
Fig. 3. —Growth of aluminum in stalk per acre of sunflower crop. Time (<) is reckoned in days from 
date of planting. Growth ( x ) is expressed as a percentage of 7.5 pounds. One observation at <=127 
and £=145 (=10.86 pounds per acre) is not included in the graph and was ignored in fitting the curve. 
Equation to curve: 
log 7^=i=0.033 (<—97) 
simultaneously with or precede that of the crude fiber. On the other 
hand, if the aluminum represents a nonessential constituent held 
mechanically by the crude fiber structures of the plant, it might be 
expected to accumulate in proportion to the crude fiber, but at a 
later time. The pronounced lag in the appearance of aluminum 
favors the view that it is associated with the crude fiber as a mere 
mechanical accumulation, rather than as an essential element of the 
plant tissues. This illustrates one use of the growth-equation con¬ 
stants, and brings out a relation which might otherwise easily escape 
detection. 
CRUDE FIBER IN STALK OF SUNFLOWER AND CORN 
The vegetative and reproductive stages of growth of annual plants 
represent two distinct aspects of the physiology of growth of the 
plant as a whole. The present data pertaining to the stalk principally 
