(1989) described a group of three stamens from the late Albian of the Potomac Group as a tripartite androecium with two pairs of microsporangia
on all three parts.
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trijurca Reproductive organs Unisexual; on the same +/+ or separate plants Pollen Small; light; non- +/+/+ clumping Pollen grains per ovule Large numbers + Microsporangia
Elevated; subtended by +/- slender elastic "beams" Ovulate structures Exposed; reduced in 1 number; attractants absent Pollen receptive Exposed and "sticky"; +/- surfaces large but dissected Plants Growing in open sights; +/?
microsporophyll: Leaflike structure giving rise to one or more microsporangia
In light of the preceding, we can accept that there is enough morphometric and observable morphological differences between Zamia stevensonii, as here presented, and the other species to which it has been compared or with which it has been mistaken to warrant its inclusion as a new species, considering the geographic range, white emergent leaves, relatively small above or below-ground stems, small number of pollen cones per plant, smaller size of ovulate and pollen cones, and having microsporangia
only on the abaxial surface of the microsporophylls.
The reproductive structures of the pteridosperms were likewise phylogenetically terminal; later the microsporangia
became aggregated into synangia and the seeds were borne on modified or unmodified portions of the frond.
(pollen sacs) on abaxial surfaces, with a simple sterile
with 500-900 microsporangia
. Megasporophylls 15-25 in a crown and with
generic level, of the trichomes of leaves, microsporangia
, and seeds.