72 
Hi si arch BulU tin No. 2 
short F 3 families are in general shorter and the tall families 
taller than the F 2 plants from which they were derived. More 
over, the range of variation of the F 2 plants grown in 1911 wa,> 
probably increased by the weather conditions, the early plants 
Fig. 18. The tallest and one of the shortest F 3 families of Tom Thumb 
X Missouri dent as they appeared in the field September 19, 1911. 
doubtless having been made shorter and the late plants taller 
than they would otherwise have been. But it must also be re- 
membered that the same influences must necessarily have been 
felt by the early and late parent stocks, thereby making the gap 
between them greater than it would otherwise have been. It is 
