516 
Journal of Agricultural Research 
Vol. XXVIII, No. 0 
nance of the fragile rachis. On first examination it seemed that those heads 
coming from the cross in which the true wild was used were more fragile, but after 
thorough drying there seemed to be no difference. The F! heads in both crosses 
have a flattened appearance similar to those of the wild type and the rachis is 
heavily pubescent, as is the case in the wild forms. The awns resemble those of 
the wild parents and the kernels have the red color of the wild forms. In shape 
the kernels are longer than those of Kubanka, but are somewhat broader than 
those of the wild forms. 
The F 2 plants which resulted from crossing the two wild types with Black 
Winter emmer were alike in each case. So far as the characters mentioned above 
are concerned, these F x plants were similar to those from the Kubanka crosses 
with the exception that the glumes of the hybrids with Black Winter emmer were 
black or grayish-black. The color is slightly lighter than that of the Black 
Winter emmer. 
THE F 2 GENERATION 
When the second generation was grown there was considerable diversity of 
form and of degree of fragility of the rachis. Some of the characters will be dis¬ 
cussed separately. 
The first character to be considered is the fragility of the rachis. Owing to the 
nature of this character, it is very difficult to classify. This is especially true if 
the material has not dried thoroughly. Some of the rachises are brittle only 
toward the tip of the head while others may be fragile the entire length of the 
head, except for a few spikelets at the base. In the wild emmer usually two or 
three spikelets at the base of the head are held rather firmly. 
Various tests were used in order to classify this material, such as natural shat¬ 
tering, readiness of breaking when the spike was shaken, or when the spikes were 
subjected to some stress, and so on. Finally, the classification was made by 
means of the above tests plus an examination of the end of the rachis segment 
under a lens. The rachis of the true wild emmer disarticulates in such a way that 
the end of the rachis segment is round and perfectly smooth. This test was then 
applied and all plants that showed disarticulation leaving the rachis segments 
with smooth round ends were classed as fragile. If the end of the rachis segment 
was broken or torn the plants were classed as tenacious. The results of segre¬ 
gation for this character in the second generation plants are given in Table I. 
Table I.— Segregation of the second generation of crosses of Kubanka durum wheat 
and Black Winter emmer with the wild and the synthetic wild emmer for character 
of rachis, shown by manner of disarticulation 
Number of plants having— 
Devia¬ 
Cross 
Fragile rachis 
Tenacious rachis 
Devi¬ 
ation 
Prob¬ 
able 
error 
tion 
divided 
by 
probable 
error 
Observed 
Calcu¬ 
lated 
Observed 
. Calcu¬ 
lated 
Kubanka X true wild. 
134 
133.5 
44 
44.5 
0.50 
3.90 
0.13 
Kubanka X synthetic wild—. 
147 
150.0 
53 
50.0 
3.00 
4.13 
0. 73 
Black Winter emmer X true wild—. 
216 
219.38 
18 
14.62 
3.38 
2.50 
1. 35 
Black Winter emmer X synthetic 
wild.. 
221 
227.8 
22 
15.20 
6.80 
2.55 
2.67 
From these results it is very evident that, so far as this character is concerned, 
the segregation for fragile and for tenacious rachis gives about the same ratio 
whether the wild or synthetic type is used as the parent. It seems evident that 
