Waxy endosperm starch from the genotype su₁ su₁ Du Du wx wx is 100% amylopectin, while su₁ su₁ Du Du Wx Wx starch is about 60% amylopectin and 40% amylose, and su₁ su₁ du du Wx Wx is about 35% amylopectin and 65% amylose. It

was conceivable that in the combination su₁ su₁ du du wx wx the gene du might interfere with the usual effect of wx so that some amylose would be formed, giving an endospem which would stain blue with iodine. This apparently is not the case. Selfed ears from four F₁ plants of the genotype su₁ su₁ Du du Wx wx each gave distinctly less than the normal 25% of red‑staining kernels, but this can be attributed to the well-known behavior of Wx wx pollen on su₁ su₁ silks. Two F₂ plants obtained from red‑staining (wx wx) kernels were selfed and also outcrossed to a su₁^am du tester to determine their genotype as regards du. The outcross ears were half sugary and half starchy, indicating that the tested plants were Du du. The two selfed ears had 301 kernels, all red‑staining. Presumably about one‑fourth of these were homozygous du, yet still produced only red‑staining amylopectin. The pollen of these two plants was also 100% red‑staining, even though half of the grains were du.

Linkage data has been obtained which adds to Mangelsdorf's evidence that du is on chromosome 10. The numbers of plants are small but the results are convincing. Translocation 4‑10b su₁ Du of E. G. Anderson was crossed with a + su₁ du line. The F₁ was backcrossed by + su₁^am du, yielding starchy seeds (su₁^am su₁ Du du) and sugary seeds (su₁^am su₁ du du). The two types were separated at planting and the following data on pollen sterility obtained:

		Pollen
Plant genotype	No. plants	Semisterile	Normal
su1^am su Du du	15	15	0
su1^am su du du	10	0	10

This is linkage of Du with the.translocation with less than 4% crossingover.

Translocation 9-10b Su₁ Du was crossed by + su₁ du and the F₁ backcrossed by + su₁ du. The resulting seeds included four endosperm types as follows:

(1) Su1 Su1 su1 Du Du du	Starchy;	smooth cap
(2) Su1 Su1 su1 du du du	Starchy;	deep cap depression
(3) su1 su1 su1 Du Du du	Sugary	not easily separable.
(4) su1 su1 su1 du du du	Sugary

Type (1) in this material was easily separable from type (2) and

the following pollen data were obtained on the resulting plants:

		Pollen
Plant genotype	No. plants	Semisterile	Normal
(1) Su1 su1 Du du	19	19	0
(2) Su1 su1 du du	19	1	18

Du again shows linkage with the translocation with 2.6% crossingover. Chromosome 10 was the common member in the two translocations used.

James W. Cameron