Stem: 2 to 3 ft. high, leafy, branched.
Leaves: Opposite, or sometimes in whorls of 3; lance-shaped, with
heart-shaped base clasping stem.
Preferred Habitat - Wet meadows, watery places, ditches, and
banks of streams.
Flowering Season - June-August.
Distribution - Eastern Canada to Delaware, and westward through
Middle States; also in Europe.
Through Darwin's patient study of this trimorphic flower, it has
assumed so important a place in his theory of the origin of
species that its fertilization by insects deserves special
attention. On page 5, the method by which the pickerel weed,
another flower whose stamens and pistil occur in three different
lengths, should be read to avoid much repetition. Now the
loosestrife produces six different kinds of yellow and green
pollen on its two sets of three stamens; and when this pollen is
applied by insects to the stigmatic surface of three different
lengths of pistil, it follows that there are eighteen ways in
which it may be transferred. But Darwin proved that only pollen
brought from the shortest stamens to the shortest pistil, from
the middle-length stamens to the middle-length pistil, and from
the long stamens to the long pistil effectually fertilizes the
flower.
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