Volume 3, Issue #2 - Cubits

The pollinaria of Eriostemma species seem to have
evolved a different mechanism for attaching themselves to
the bodies of visiting pollinators. In Hoya species, the pollinaria
are formed on the corona with their pollina held out
straight, extending towards the center of the corona (figure
4). When the pollinia are pulled from their positions over the
stigma, the pollinia usually spring inwards, crossing each
other and forming a clasp in which a portion of the pollinators
body may be trapped (figures 5 & 6- the red dots indicate
the likely place where a pollinators leg or proboscis
would be trapped.)
In Eriostemma species, the pollinarium hold their pollinia in
a different position, the base of each held far out from the
corpuscula, the pollinia apex angled inwards, almost touching
(figure 1). When Eriostemma species pollinaria are removed
from the stigma, the pollina tend to swing away from
each other, rather than towards each other, as in Hoya, possibly
due to the twisted nature of the translators/caudicles. In
figure 2, the top pollinarium has both pollina sprung into
their secondary position, the lower two have one each of
their pollinia swung to their secondary position. No studies
seem to have been done to determine the actual method of
polliarium transfer for Eriostemma, but it seems logical that
the likely place for attachment to a visiting pollinator for
these species would be in the complexly twisted translators/
caudicles themselves (figure 3, with two red dots highlighting
the likely place of attachment). n
28