ss E. LINDHARD 
© (4 Sp: de Sp€) Oe OA NB Spe). = ‘ 
12 Sqh. het.: 4 Spelt. het.: 1 Typ. comp.: 3 Short comp., 
the ratio in which the Squarehead heterozygote generally segregates. 
Here again the formula does not account for the fact that Short com- 
pactum and even Sgh.-heterozygote gives »Normal» gametes. 
14. A different scheme of segregation is followed by Compactum 
when heterozygous in the factor for awns (Tab. 24), the ratio of 
awned to awnless Spelt.-heterozygotes being very variable in this case 
thus excluding the assumption that the factors u and Sp should be 
located in the same chromosome. When awned and awnless plants 
are added, instead of the ratio f. i. 9 Norm. : 3 Sp. het.: 9 Typ. Comp. 
: 1 Short. comp. we get about 6 Norm.: 10 Sp. het.:6 Typ. comp. :1 
Short comp., indicating an interruption in the binding between the u 
and Sp and the Sp and C as well. The Uu Squarehead-heterozygotes 
give similar results. . 
15. The Perenne type segregates in one case directly from a 
Spelt.-heterozygote line of common type and independent of the Spel- 
toid-complication giving Squarehead- and Speltoid-spikes when the 
mother-line is a Spelt.-heterozygote but Squarehead-spikes only when 
it is of Normal type. However the two late flowering types Dwarf- 
and Late »common» wheat, both segregating in a heterogamous scheme, 
segregate Perenne as well. 
16. The above summary shows the extensive variation in the pro- 
geny of one single Speltoid mutant, but what should be the expected 
frequency of such mutations? When all the offspring of plants of 
Normal type is summarised, in a total progeny of 14288 plants 28 
Speltoid-heterozygotes and 9 Compactum appear. While in homozy- 
gous awned or awnless lines the number of mutants is only 1 in 600, 
in the Uu-heterozygotes we get 1 mutant in 150 Normal plants. Do 
new factors appear in all these mutants or do they only represent com- 
binations and recombinations of old facters? 
17. With the assumption of a linear location of genes in the 
chromosomes, as found in Drosophila, there still might be differences 
of great importance in the construction of the cell nucleus in this or- 
ganism and in the wheat. In the sub-species of cultivated wheat the 
haploid number of chromosomes can be written x = na; according to 
Kinara for T. monococcum x — 7, for T. dicoccum and other sp. x 
— 2 7 and for T. vulgare, T. Spelta and T. compactum x = 3 X 7. 
The chromosomes show great persistence also in the genes they carry. 
It therefore seems plausible to assume that species with x = na are 
