592 
Journal of Agricultural Research 
Vol. XI, No. ii 
dead before the first-generation plants began wilting (PI. 45, A, B). 
Later all of these plants would perhaps succumb to the disease. 
In some of the experiments there was segregation in the first-generation 
offspring, part of the plants wilting, while others were as resistant as the 
resistant parent. In this case there was an intermediate condition as 
to the time of infection of the F* plants also. This fact was apparently 
not due to excessive vigor of the plants, since vigor seems to play no part 
in the resistance to wilt by the flax plant. The plants of common flax 
seem to be even more vigorous than resistant plants in cases, but suc¬ 
cumb very readily to the attacks of the fungus. 
No such simple ratios were obtained from these flax crosses as Biffen 
(2, 3) reported from his wheat crosses. Biffen was studying the nature 
of the inheritance of resistance by wheat to yellow-rust. In his first set 
of experiments (2) he crossed Rivet wheat, which is resistant to yellow- 
rust, with Michigan Bronze, which he states is probably more suscep¬ 
tible to yellow-rust than any other wheat in existence. The first genera¬ 
tion from this cross was entirely susceptible to attacks by the rust. No 
seed was obtained for a sesond generation, owing to the severity of the 
attack. Red King, a very susceptible variety, was crossed on Rivet, 
and the first generation was susceptible in this case also. A second gen¬ 
eration from these plants gave practically a i-to-3 ratio, which Biffen 
interpreted as indicating that resistance and susceptibility are unit char¬ 
acters, the latter being dominant to the former. Biffen fails to state just 
where he drew the line between resistance and susceptibility, a very 
important point. He says the plants which he placed in the resistant 
group were “relatively” or “almost” free from rust. He also states 
that the third generation gave results which confirmed those of the pre¬ 
ceding generations, but, that statistics for this last generation were not 
altogether satisfactory, owing partly to the limited amount of grain har¬ 
vested for the trial and partly to the unfavorable conditions at the time 
of sowing. 
In 1907 Biffen (3) published on a piece of work which was much more 
thorough apparently than his first work. He reported in this case, as 
before, that the first generation of wheat plants from a cross between 
entirely immune and susceptible strains was entirely susceptible, and 
that the second generation gave approximately a ratio of one resistant to 
three susceptible plants. In these experiments every plant that showed 
symptoms of rust was considered as suscept ible. He also states that there 
was a gradation between entirely resistant and entirely susceptible 
plants. 
Stuckey (22 ), working with tomatoes at the Georgia Station, states that 
by crossing the Red Cherry, which is resistant to blossom endrot, with 
the Greater Baltimore, a large commercial type which is susceptible to the 
disease, both the first and second generations from the cross were resist¬ 
ant to blossom endrot and that there was no segregation in the second 
