IDENTICAL-TWIN HYBRIDS OF CITRUS X PONCIRUS FROM STRICTLY SEXUAL SEED PARENTS

A B S T R A C T Tree characters of 13 sets of twin and triplet hybrids from single seeds of crosses of Citrus X Poncirus and characters of three other Citrus twin sets are described. Evidence from tree size and habit, leaf size, shape, and thickness, and time of leafing and leaf fall indicates that these twins and triplets are probably all genetically identical within sets. Recent cytological evidence is cited which indicates that supernumerary sexual embryos can occur in Citrus by a process of budding from the primary embryo. The twin and triplet hybrids are clearly of separate origin from multiple asexual seedlings, also normally genetically identical, which arise fram cells of the nucellus in many Citrus varieties. MVANY MEMBERS of the genus Citrus and some closely related genera reproduce asexually by