Revision of Passiflora Subgenus Decaloba ... - Passion Flowers

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(Thomas 2032, 2034) and was listed as a rare plant in the 1997 IUCN Red List of
Threatened Plants (http://www.unep-cmc.org/species/plants/red_list.htm). It is
my opinion that its status should be upgraded to extinct/endangered. It is
fortunate that MacDougal obtained cuttings of P. macfadyenii from Thomas
(MacDougal 452, Thomas 2032) and grew the plant in the greenhouses at Duke
University from 1979-1982; they are no longer in cultivation. Thanks to their
efforts we have a better understanding of the biology of this very rare taxon.
Passiflora macfadyenii appears to be self-incompatible, as no fruits were
produced from ca. 30 controlled self-pollinations performed in the greenhouse by
MacDougal (MacDougal 452). In addition, no fruits were produced by autogamy
during the ca. four years that it was in cultivation by him.
In an unpublished manuscript, MacDougal determined the total sugar
concentration measured as sucrose equivalents in percent weight per total
weight to be 29-44% in P. macfadyenii. He also found the flower to have no
odor. The flower shape and morphology, combined with these data, indicate that
P. macfadyenii is (or was) likely utilized by hummingbirds.
Dried leaf samples of MacDougal 452 were chromatographically screened by
McCormick for flavonoids. Detectable levels of flavonol 3-O-glycosides were
found but no C-glycosylflavones (McCormick, 1982).