Com Investigations 
95 
The relatively greater immediate increase in weight of the 
embryo than of the endosperm upon crossing elemental strains 
would necessarily seem to be due either to the difference in 
chromosome relationships within the two parts or else to a 
difference in their relative nutrition. 
The cause of the difference in relative development seems 
more likely a matter of nutrition. The small leaf area, reduced 
root development, and sluggish synthetic activities of the inbred 
plant may result in a somewhat undersuppty of plant nutrients. 
In such event, the full development of the embryo, which is the 
vital element in reproduction, might be favored at the expense 
of the endosperm. The endosperm is a mere food supply for 
the embryo and may be somewhat more heavily drawn upon 
even at this stage as a result of the stimulated growth of the 
embryo. 
Chaet 3. — Immediate effect of crossing upon the kernel development of 
pure lines (inbred) and ordinary commercial varieties. (In case of 
the varieties, “pure” kernels refers to those kernels fertilized by 
pollen of the same variety.) Data taken from Table 37. 
