Abstracts of Papers Presented at the 1949 Meetings of the Genetics Society of America.

S OF PAPERS PRESENTED AT THE 1938 MEETINGS OF THE GENETICS SOCIETY OF AMERICA RICHMOND, VIRGINIA, DECEMBER 28-30, 1938 E. W. LINDSTROM, Secretary Ames, Iowa ANDERSON, R. L., and WHITING, P. W., Johnson C. Smith University, Charlotte, N. C. and University of Pennsylvania, Philadelphia, Pa. : Present status of linkage groups in Habrobracon.-Alleles and linked genes with direction right or left undetermined are given in parentheses following symbols. The X-linked group with map distances is SK-13-r(r*)-17-gl-38-f~ (-1o-X)-22sb(sba). Orange group is o(ol, od, oi)-11-m-28-K(K8, K c ) . Small-wings group is cp-16-sv (-23-td-27-ma)-24-sw. Red group is gy (-4-ac-4-el)-4o-rd-34-ct. White group is wh(wlz”)-Io-st. Cantaloup group is bl-27-le-I I-c-IS-I-3-”-13ho-9-vl-5-cw-I 5-ro-rz-bu-37-cr (-Is-&) -40-sl-0-CO. Data suggest that cantaloup group (187 units) may be loosely linked with red and with white but results are contradictory (translocations?). There is interference in regions SK to gZ of X group and le to vl of cantaloup group, but mortality differences make exact determinations unreliable. BERGNER, A. D., AVERY, A. G., and BLAKESLEE, A. F., Carnegie Institution of Washington, Cold Spring Harbor, N. Y.: Sectorial chimeras, chromosome deficiencies and doubling of chromosome number in Datura stramonium induced by colchicine treatme&.-Over 2,000 plants were recorded from seeds treated for 3 to 8 days with 0.2 and 0.4 percent colchicine. From higher dosages from so to 75 percent were abnormal (mostly plus or minus 4n) of which nearly half show one to four aberrant sectors. Nearly 200 cytological determinations have been made from selected off-type diploids, tetraploids or higher polyploids. Among “diploids,” seven types had 2n-I chromosomes. Among over roo “tetraploids” (4n=48) the count went as low as 42; one third had 47 chromosomes; one fifth had 46. In tetraploid Daturas there are 12 sets of four chromosomes each. In 46 or less-than-46 chromosome types, one or two chromosomes may be missing from the same set. No set was found with less than two chromosomes. Among 46 chromosome types, I I showed two chromosomes missing from a single set and 2 showed one chromosome missing from each of two sets. Apparently chromosomes are frequently eliminated before doubling takes place. Such “tetraploid” plants should give partial disomic inheritance. That elimination of chromosomes also follows doubling is shown by the large number of 47 chromosome types as well as the loss of univalents in some of the less-than-47 chromosome types. The largest chromosome appears most frequently eliminated. Higher numbers ranged from 56 to 96. Two types showed a chromosome fragment, one with 47 and one with 45 additional chromosomes. GENETICS a4: 65, Jan. rp39