390 
Journal of Agricultural Research 
Vol. IX, No. ii 
respect to these characters would be T'T'RR. Half-tunicate plants, such 
as the male parent of the hybrid, would be TT'RR. In a cross between 
such a plant and ramosa the first generation would consist of two kinds 
of plants, TT'RR' and T'T'RR'. Since all contain /?, which is dominant, 
none would be ramosa . One half being heterozygous, for T would be 
half-tunicate, the other half would be nontunicate or normal, being 
homozygous for T'. Since the tunicate plants of the first generation 
are heterozygous for both T and R, the selfing of such individuals would 
give all possible combinations (Table I). 
Table I .—Gametic composition of the hybrid between Zea ramosa and Zea tunicata 
Parents . Zea tunicata. Zea ramosa . 
Gametes. --TR T'R T'R' 
Ft 
Zygotes. 
Gametes 
f r : > 
TR 
TR' 
T'R 
T'R' 
T'R 
T'R' 
TR 
TR 
TR 
Full tunicate 
TR' 
TR 
Full tunicate 
T'R 
TR 
Half tunicate 
T'R' 
TR 
Half tunicate 
T'R... 
T'R 
T'R 
Normal* 
T'R' 
T'R 
Normal 
TR' 
TR 
TR' 
Full tunicate 
TR' 
TR' 
Tunicata - 
ramosa 
T'R 
TR' 
Half tunicate 
T'R' 
TR' 
Tunicata- 
r antes a 
T'R'.. 
T'R 
T'R' 
Normal 
T'R' 
T'R' 
Ramosa 
T'R 
TR 
T'R 
Half tunicate 
TR' 
T'R 
Half tunicate 
T'R 
T'R 
Normal 
T'R' 
T'R 
Normal 
T'R' 
TR 
T'R' 
Half tunicate 
TR' 
T'R' 
Tunicata- 
ramosa 
T'R 
T'R' 
Normal 
T'R' 
T'R' 
Ramosa 
From the above hypothesk and the behavior of the first generation, 
we should assume that in F 2 all plants homozygous for R' would be 
ramosa. All plants either heterozygous or homozygous for R and homo¬ 
zygous for T' would be normal. Those heterozygous for T and with 
at least one R would be half tunicate. Those homozygous for T and 
with at least one R would be full tunicate. Since the above condi¬ 
tions are not mutually exclusive, there would be combinations calling 
for the plants to be ramosa and at the same time either full or half 
tunicate. 
There were 326 second-generation plants from the Z. tunicata first- 
generation ears. The observed number compared with the number 
expected in accordance with the gametic composition assumed above 
are given in Table II. 
