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Summary
Rudbeckia speciosa Wender. is a tetraploid species (2n=4x=76) that spreads by apomitic methods. The » semigamy « (that is » the autonomous division of the male nucleus in the cytoplasm of the egg «) occur in 79% of the unreduced gametophytes (56% with endosperm, 23% without endosperm) and the apogamy (»stimulated apogamy« the embryo development requires the stimulation from pollen tube) occur in 21% (15% with endosperm, 6% without endosperm).
The endosperm requires fertilization for its development and begins to develop before the embryo.
Not uncommonly the secundary uncleus remains undivided even when the embryo is multicellular, although seeds cannot arise without endosperm.