Howes, Paul B . Stem brittleness in homo - Plants homozygous for hl (hairless) zygous hl plants caused by storied also have a brittle stem (Butler, J . xylem . Hered . 43:32) . Microscopical exami nation of tangential sections of both normal and brittle stems reveals that the former has essentially non - storied wood while the latter has a distinctly storied arrangement of xylem cells . It is reasonable to assume that the storied xylem in homozygous hl plants is the direct cause of stem brittleness . An underlying relationship between the lack of trichomes and storied xylem, pleiotropic effects of the hl gene, has yet to be elucidated . Kerr,E . A . Linkage relations of imb - irr - y Irregularis (irr) was assigned to on chromosome 1 . chromosome 1 on the basis of small F 2 populations showing linkage between it and y (Kerr TGC 14:16) . Soost (TGC 18:4) grew F 2 populations segregating for irr but did not report any data . Linkage relations of imbecilla (imb) have been reported by Rick and Boynton (TGC 13:40 - 42) and Philouze (TGC 23:28 - 29) who placed it 23 and 34 units respectively from y . Zobel (TGC 22:30) placed imb 79 units from y but apparently did not study imb specifically . Presumably because of these discrepancies, imb is not given a location on the latest map (TGC 30:3) . Kanwar, Kerr and Harney (TGC 30:20 - 21) reported that imb was about 17 units from Cf - 1 and Cf - 4 which have been assigned positions 62 and 64 units respectively from y . My 1980 results with imb - y were not consistent (Table 1) since one population in coupling gave 31% crossovers and the other 50% . Previous studies with populations in