Cup-shaped nectaries
("extra nuptial") are situated on the upper side and near the
base of the leaf stalks on these cassia plants, where they can
have no direct influence on the fertilization of the blossoms.
Apparently, they are free lunch-counters, kept open out of pure
charity. Landing upon the long black anthers with pores in their
tips to let out the pollen, the bumblebees "seize them between
their mandibles, says Professor Robertson, "and stroke them
downward with a sort of milking motion. The pollen...falls either
directly upon the bee or upon the erect lateral petal which is
pressed close against the bee's side. In this way the side of the
bee which is next to the incurved petal receives the most
pollen.... A bee visiting a left-hand flower receives pollen upon
the right side, and then flying to a right-hand flower, strikes
the same side against the stigma." When we find circular holes in
these petals we may know the leaf-cutter or upholsterer bee
(Megachile brevis) has been at work collecting roofs for her
nurseries (see Hairy Ruellia).
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