STUDIES OF MEIOSIS IN THE GENUS SAXIFRAGA OF THE PACIFIC NORTHWEST

Abstract

A cytogenetic study of the genus Saxifraga in the Pacific Northwest has been initiated as a contribution toward a better understanding of relationships within the genus. The present paper reports work done on nine species or groups of morphologically similar species and varieties (each group termed a "plexus") which have so far been studied. The nine species or groups of species are S. tolmiei, S. bronchialis, S. integrifolia, S. ferruginea, the S. montanensis plexus, the S. occidentalis plexus, S. odontoloma, S. lyallii and S. mertensiana. Meiosis in pollen mother cells of one species was found to be generally regular, pollen fertility high. In every other species or plexus a variable and sometimes very high degree of meiotic irregularity was present. Pollen fertility was often much reduced. The cause of meiotic disturbances has not yet been discovered. Consideration is given to the ways in which the species may succeed in spite of reduced pollen fertility. Such irregular meiotic divisions would be difficult to use in cytogenetic studies as a standard for comparison with meiosis in artificial hybrids.