594 
Journal of Agricultural Research 
Vol. XI, No. ii 
were grown in winter and early spring, when the temperature was con¬ 
siderably lower. A slight rise in temperature serves to accelerate the 
growth of the fungus, and the disease becomes more severe. 
TabIvE III.— Resistance to flaxwilt obtained from the progeny of a cross between resistant 
flax No. 4$ , and susceptible No. 3 <$ a 
Parent strain. 
Date of planting. 
Num¬ 
ber of 
plants 
grown. 
Ratio at end of 
three weeks. 
Wilted. 
Not 
wilted. 
Ratio at end of 
experiment. 
Wilted. 
Resist¬ 
ant. 
Num¬ 
ber of 
plants 
killed 
by 
wilt. 
4D2o(Fj). 
Resistant No. 4. . 
Susceptible No. 3. 
F 2 generation: 
4D20-1. 
4D20-2 
4D20-3. 
4D20-4. 
4D20-5. 
4D20-6. 
4D20-8. 
1916. 
Feb. 2.. 
_do.. 
_do.. 
July 22. 
Sept. 23 
....do.. 
_do.. 
.do.. 
.do.. 
_do.. 
Total 
Resistant No. 4. . 
Susceptible No. 3 
Sept. 23 
_do., 
26 
39 
52 
68 
98 
”5 
28 
101 
5 ° 
70 
530 
56 
82 
o 
o 
34 
37 
42 
40 
9 
59 
29 
54 
6 
76 
26 
39 
18 
o 
o 
52 
3i 
56 
75 
19 
42 
21 
16 
45 
62 
68 
22 
76 
34 
61 
270 | 260 
368 
50 
6 
10 
82 
26 
39 
23 
36 
47 
6 
25 
16 
9 
162 
46 
o 
o 
o 
52 
40 
53 
47 
19 
64 
30 
53 
306 
6 
82 
a 9“female; c?=male. 
Since the first generation from this particular cross was entirely 
resistant, it was hoped that some reasonable explanation might be given 
for the results obtained in the second generation, although it was appar¬ 
ent at once that they could not be explained on a unit-factor basis. As 
the number of susceptible F 2 plants was very large, it was thought that 
they might be explained by Little’s (16) hypothesis, which is an expla¬ 
nation of cases that appear to be a reversal of dominance. The indi¬ 
viduals showing the character in question decrease in number in the 
F 2 generation, as there is an increase in factors which produce the par¬ 
ticular character. The general principle is that with the addition of 
each factor involved the number of F 2 individuals possessing the char¬ 
acter in question is multiplied by 3, while the total number of F 2 indi¬ 
viduals is multiplied by 4. The difference between the number of indi¬ 
viduals with the character and those lacking it grows progressively 
greater with each factor added. With the flax cross under considera¬ 
tion, the first generation was entirely resistant to wilt. In the second 
generation, from a total of 530 plants 162 were resistant and 368 suscep¬ 
tible. These figures approach very closely the expectation, if four factors 
are concerned in producing resistance. The actual expectation would be 
81 resistant to 175 susceptible, which is a ratio of 1 to 2.16. The actual 
proportion obtained was 81 resistant to 184 susceptible, which is a ratio 
