Meiosis inAllium fistulosum, Allium cepa, and their hybrid

Abstract

does not appear. First page follows. A Preceding paper(4) discussed the general morphology of several varieties of Allium. cepa L., Allium fistulosum L., and their hybrids. Because of the high degree of self-sterility in the hybrid, cytological studies were begun in 1932 in the hope that they might explain the cause of sterility and possibly indicate whether a stable derivative combining the desirable characters of the two species might be secured. These investigations have now been completed on the Yellow Globe Danvers variety of Allium cepa (pedigree 15-108-1), on a strain of fistulosum (37-1), and on their hybrid. Methods To secure material containing pollen mother cells at desirable stages, an anther was first crushed in aceto carmine and examined under low power. If suitable division figures were found, the remaining five anthers of a flower were removed and fixed, for at least 24 hours, in a solution of 25 per cent acetic acid and 75 per cent absolute alcohol. They were then transferred to 80 per cent alcohol, where they may be kept indefinitely. Material stored for four months and then stained has given better differentiation between chromatin and cytoplasm than material used a few days after fixing. When preparations were made from fixed material, an anther was placed on a slide and covered with a small drop of aceto carmine. The aceto carmine had to contain a considerable amount of iron; otherwise the chromosomes were stained very weakly, and differentiation was not sharp. A curved, blunt needle was used to press out the pollen mother cells, and the anther wall and all other débris were carefully removed before the cover slip was added. All excess aceto carmine was wiped off, the slide examined under low power, and its preparation completed under observation. Usually the cells were found in masses scattered over the slide.