70 
Research Bulletin No. 
All the F 3 families from which data are at hand came from a 
single F 2 fraternity, No. 510, which, of course, came from a single 
F-l plant, and this plant from the nnion of a single gamete from 
each of the parents. Whether all the other gametes produced 
by those two parent plants were like the two concerned in this 
cross or whether they were of several different sorts can obviously 
have no bearing on the behavior of the one F 1 plant, the single 
F 2 family, and the several F 3 families in question, because these 
other sorts of gametes, if there were such, had no connection 
Fig. 16. Height of plants of the shortest and tallest F, families of Tom 
Thumb pop X Missouri dent as grown in 1911. 
with this line of progenies. In other words, the possible, or 
even probable, fact that the parent plants may not have been 
homozygous in all size factors can in no way lessen the impor- 
tance of the principal conclusions to be drawn from this and sim- 
ilar tables. There is no escape from the fact that segregation in 
F 2 occurs with respect' to size factors just as truly as it does with 
factors for other characters. There is also no getting around 
the plain indications derived from the F s progenies that F 2 size 
segregates man serve as the basis of permanent, true-breeding 
tjiyes just as in <-asc of various other Mendelizing characters. 
