Chromosome Behaviour of Triploid Œnothera

Abstract

IN two recent issues of NATURE, Darlington¹ and Gates² have entered into a discussion of synapsis in triploid Œnotheras. The root of controversy lies in the novel observation and interpretation of Catcheside³ that a continuous ring of 21 chromosomes was formed in a triploid plant. Having been engaged for the past two years in an investigation dealing with the genetics and cytology of triploid Anotheras, I have naturally focused my attention on all published accounts of polyploidy, particularly those which deal with chromosome behaviour in triploids. At the suggestion and under the guidance of Prof. G. H. Shull I undertook the studies of triploid Ånotheras, the origin of which he has described in a recent paper.⁴ Fifteen triploids were turned over to me in the fall of 1928 and their cytology was studied. I have since then made cytological analyses of buds of triploids in the summers of 1929 and 1930. The triploids studied in the last two years have all been derived from pure (Œ. Lamarckiana. As the chromosome behaviour in triploid (Ánotheras has become an issue of lively interest, I report here such observations as are pertinent to the fundamental point under discussion. My observations were based on paraffin sections stained with Heidenhain's iron-hæmatoxylin and on smear preparations of pollen mother cells stained with iron-Brazilin.⁵ My microscopic preparations have been examined both by Prof. E. G. Conklin, under whose supervision I have acquired my cytological technique, and by Prof. Shull.