Rumex Lunaria L., a Gynodiœcious Tetraploid Species

Abstract

THE genus Rumex is divided by modern taxonomists¹ in three sub-genera : Lapathum, Acetosa and Acetosella. In the sub-genus Lapathum only hermaphroditic species occur, but in the other two sub-genera diœcious forms are met. According to studies on the mechanism of sex determination met in these two latter sub-genera, the sub-genus Acetosella belongs to the Melandrium type of localization of sex-determining genes, that is, the Y possesses strong male elements, which may dominate over all the female elements in the X's and autosomes in the tetraploid, hexaploid and octoploid species of the subgenus^2,3. The diœcious species of the sub-genus Acetosa, however, are found to belong to the Drosophila type of localization of sex-determining genes, that is, the Y's are inert, and the sex is determined by a balance between the X's and the autosome sets^4,5,6. This latter mechanism prevents polyploidy, as shown by Bridges⁷, Muller⁸ and Ono⁴. The diœcious plants of the sub-genus Acetosa belong to the section Euacetosæ, but in the section Hastati polygamodiœcious and gynodiœcious species are met³. Hermaphroditic plants are met in other sections of the sub-genus, namely, Scutati and Vesicarii. Polyploidy has hitherto been known only within the British forms of the collective species R. scutatus⁹.