Polyploidy is a conspicuous feature of chromosomal evolution in higher plants. Stebbins (1) estimates that between 30 and 35 percent of flowering plant species have gametic chromosome numbers in multiples of the basic number characteristic of the genus to which they belong. Polyploidy is common in some groups and rare or absent in others. Levin and Wilson (2) calculate that relative increase in chromosome diversity in woody angiosperms is about 14% that of herbaceous angiosperms. Habit, habitat and the breeding system seem to contribute to origin and success of polyploids.
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