92. The cytological identification  of the chromosomes associated with the
`R-golden' and ' B-liguleless' linkage groups in Zea mays. Barbara McClin-
tack and Henry E. Hill, Cornell University.
The smallest chromosomes of the normal set (Science, vol. 69, p. 629, 1929)
carries the gene of the r-g linkage group.  `2n + 1 plants triplex for this chromo-
some give trisomic ratios for the factor pair R-r when selfed, sib-crossed, and
back-crossed.  These plants showed disomic ratios for c-wx, .su, 6, y, gk-w6, pr,
and a. Plants triplex for the r-g chromosome differ only slightly in appearance
from the normal diploids. In 2n +l plants the extra chromosome is transmitted
through one-third of the eggs. Only a small percentage of n + 1 pollen grains
function in competition with n. grains (rr? X BRr 2 gave 941 colored to 486
colorless kernels, 2: 1 expected; rr 0 X Rrrd gave 1392 colored to 2685 colorless
kernels, 1: 2 expected).  The fourth largest chromosome carries the genes of
the b-Zg linkage group. 2% + 1 plants triplex for this chromosome give trisomic
ratios for v,, b, and lg.  These 2n + 1 individuals show a markedly decreased
vigor. The extra chromosome is carried through one-fourth of the eggs, but is
seldom transmitted through the pollen (lglg 0 X LgLglg d gave 344 Lg : 163 lg,
2: 1 expected; lglg 0 X Lglglg d gave 276 Lg : 542 lg, 1: 2 expected).  The
gene& investigations have been undertaken with the cooperation of Marcus M.
Rhoades and George W. Beadle.