Classically, the Platyopuntia (prickly pears) include the flat-stemmed members of the
the genus Opuntia (Cactaceae). The members of this subgenus (which freely hybridize)
are widespread throughout arid regions of the New World. Currently, the
genus Opuntia is divided into the Cylindropuntia (chollas),
Opuntia (now the prickly pears), Grusonia (club chollas), and
Nopalea and Consolea - rare taxa found only in Florida.
"Platyopuntia" is used here, due to the current widespread usage
of "Opuntia" to refer also to the chollas, whose pollen is distinct from
that of the prickly pears. The term should be abandoned when (if?) the new systematics
achieves general acceptance.
Pollen light micrograph:
Generally large, 30 - 100 µm, fenestrate, reticulate pollen grains, generlly
with polygonal outlines. Sculpturing elements are apparent in the lumina, and on
the floors of the fenestrae.
The pollen of the various species (if taxonomists can agree that they exist)
probably can be determined by size, with larger grains showing a square or hexagonal
pattern of fenestrae, and smaller grains with a triangular pattern (see.
Opuntia chlorotica [silver dollar cactus] below).
Opuntia engelmannii pollen is dimorphic, with about 1 % of the grains
being small (¼ normal size) and inaperturate (shown at right).
Pollen scanning electron micrograph (SEM)
Note the then membranes on the floors of the fenestrae,
which may serve as egress for the pollen tube.
Production and Dispersal:
Low production and poor dispersal for these insect-pollinated species. The flowers are
visited by a host of beetles and solitary bees.
The thick wall is resistant to deterioration, but the large grains often break apart.