466 
Journal of Agricultural Research voi.xxin.No. 6 
in the two F 3 ’s that the figures in Table IV or the curves in figure 
i do not show clearly, namely, that transgressive segregation occurred 
in the F 3 generation of Fortyfold X Turkey, there being five rows 
decidedly more resistant than Turkey and many rows more susceptible 
than Fortyfold. This phenomenon was not observed in the other F 3 
generation, in 1918. Turkey was just as resistant and Hybrid 128 
just as susceptible as the extremes of the segregates. This suggests 
the idea that Fortyfold carries an element of resistance different than 
the elements of resistance in Turkey, which, added to it, produces a 
wheat more resistant than Turkey, and without which the segregate 
becomes as susceptible as Hybrid 128. In susceptible segregates this 
Fortyfold element of resistance has a value of from 10 to 20 per cent, 
but in resistant segregates the value lies between 1 and 7 per cent, 
depending upon the season. It will require tests in later generations 
to establish this hypothesis beyond question, and this is being done. 
It is difficult to place these phenomena of inheritance on a factorial 
basis on account of the seasonal fluctuations and the quantitative and 
comparative nature of the material. It is quite evident, nevertheless, 
that Turkey has several times as much resistance to bunt as Fortyfold. 
It is also evident, from the performance of the segregates of Turkey X 
Hybrid 128 in the F 4 and F 5 generations, that this “Turkey resistance” 
splits up into its component parts when crossed with other wheats of dif¬ 
ferent constitution. Table V shows the comparative resistance of 144 
F 4 rows (the offspring of 144 F 3 plants, selected from nine different F s 
rows), in comparison with the parent rows from which they came. 
The nine F 3 rows from which the selections were made were the most 
resistant segregates of beardless, club, winter hardy type (characters 
which were also being studied). It has been shown in an earlier paper 
(14) that resistance in this cross is not linked with the external charac¬ 
ters studied. In comparing the third column, “Bunt in F s generation” 
with the others, it must be borne in mind that these figures were obtained 
in 1918 and that the F 4 percentages were obtained in 1919, in which year 
(according to Table III) the parents showed 18.4 per cent more bunt 
than in the year in which the F 3 generation were tested. 
TablS V. — Distribution of bunt resistance of Turkey X Hybrid 128 in the F 4 generation 
from g resistant F 3 rows 
F3 row No. 
Number of 
plants se¬ 
lected from 
each row. 
Average 
number of 
F< plants 
per row. 
Bunt in F3 
generation. 
Average 
bunt of F« 
Range of bunt in F4 
rows. 
rows. 
Lowest. 
Highest. 
1387. 
26 
71 
Per cent. 
1.9 
Per cent . 
12. 7 
Per cent . 
5.6 
Per cent. 
35 *o 
1304 . 
22 
56 
4.8 
18.7 
6.5 
39*6 
1310. 
2 
50 
6.4 
32.0 
25-9 
38. 1 
1353 . 
14 
66 
6.6 
13- 6 
5-6 
25*4 
131 2 . 
29 
63 
7.0 
13. 2 
4-3 
26. 7 
1284. 
12 
70 
7 -1 
25*3 
12. 7 
40.3 
1297 . 
14 
42 
9.8 
33-2 
11. 6 
59*5 
I 357 . 
8 
69 
13-4 
26.6 
16. 6 
41.7 
1299. 
17 
46 
14. 6 
34. 8 
iS*S 
54*7 
Average. 
16 
59-2 
8.0 
2 3-3 
11. 6 
40. 1 
