Ricerche Cariologiche e Embriologiche Sul Genere Rudbeckia (Asteraceae)

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Abstract
The microsporogenesis of Rudbeckia laciniata L. is abnormal. The heterotypic division rests at the metaphase, by always giving »a restitution nucleus«. Such a nucleus divides itself (homeotypic division) often forming diads, very seldom triads, or monads (owing to a restitution nucleus also in homeotypic division, that is the formation of » a birestitution nucleus «, tetraploid). The ripe pollen is almost enterely degenerated. Many anomalies of degenerancy have been noticed. The formation of a birestitution nucleus is a new type of abnormal microsporogenesis: the »Rudbeckia laciniata type «.