1. An abstract on crossover chromosomes in unreduced gametes of asynaptic maize was published in Genetics, 1947, in which it was stated that the diploid egg cells, presumably arising from sporocytes with all or nearly all univalent chromosomes at metaphase I, contained crossover chromosomes. Our studies on the genetic constitution of diploid gametes from asynaptic plants have been continued and the data now at hand would seem to permit the following conclusions to be drawn: For regions in both chromosomes 2 and 9 there is a significant increase in the amount of crossing over in asynaptic plants. This is true for both haploid and diploid gametes. As an example, the frequencies of crossover and noncrossover strands in haploid gametes for two regions in chromosome 2 are given below.

Asynaptic plants		Normal sibs	% recombination
(0) Ws Lg Gl	230	339
(0) ws lg gl	239	305	ws-lg	lg-gl
(1) Ws lg gl	62	81	as 20.1	30.5
(1) ws Lg Gl	64	64	As 14.7	21.1
(2) Ws Lg gl	115	106
(2) ws lg Gl	100	103
(1-2) Ws lg Gl	21	1
(1-2) ws Lg gl	25	1
	856	1000

The most striking difference among haploid gametes from asynaptic and normal plants is the great increase in the frequency of double crossovers in asynaptic plants. The analysis of diploid gametes is slot, and comparatively little data have been obtained, but it is obvious that in these diploid eggs the frequency of crossover strands also is very high. Comparable results have been obtained for the C-sh and sh-wx regions in chromosome 9.

M. M. Rhoades and

Ellen Dempsey