Evidence on spiral structure and chromosome pairing in osmunda regalis L

Abstract

The present work is in the nature of an essay on certain aspects of chromosome structure which have been impressed upon me by prolonged study, with a variety of technical methods, of chromosome behaviour in one plant, Osmunda regalis . The tissue to be examined has been principally that of the developing sporangium, supplemented by observations on roots and prothalli, which, however, will not be referred to on this occasion. The sporangium itself offers ample material for the study of both mitosis and meiosis since the development from the young archesporium to the ripe spore is a rapid and continuous one. The technical methods employed are principally three, that of sections, that of the aceto-carmine squash (Manton 1937), and Sax and Humphrey’s modification of the ammonia method for spiral structure. Each of these methods if used by itself has limitations which necessarily result in an incomplete picture; each, however, has certain powers peculiar to it, and, as will be shown, the dovetailing together of information from all three provides a body of evidence which to me personally has been most illuminating. I am, however, fully conscious of the innumerable pitfalls with which the subject abounds and am prepared to find that some of my observations and deductions may need modification. Nevertheless, since a comparable body of evidence does not appear to exist for any other cytologically worked organism the risk of error is perhaps worth taking.