This section is from the book "Nature's Garden", by Neltje Blanchan. Also available from Amazon: Nature's Garden; An Aid To Knowledge Of Our Wild Flowers And Their Insect Visitors.
Flowers - Very small, dull green on outside; vivid, shining brownish purple within; borne in almost leafless terminal clusters on slender stems. Calyx 5-parted; corolla of 5 rounded lobes, the 2 upper ones erect, side ones ascending, lower one bent downward; 5 stamens, 4 of them twin-like and bearing anthers, the fifth sterile, a mere scale on roof of the globular corolla tube; style with knot-like stigma. Stem: From 3 to 10 ft. high, square, with grooved sides, widely branching. Leaves: From 3 to 12 in. long, oblong, pointed, coarsely toothed, on slender stems, strong smelling.
Preferred Habitat - Moist, shady ground. Flowering Season - July - September.
Distribution - New York to the Carolinas, westward to Tennessee and Kansas; possibly beyond.
An insignificant little flower by itself, conspicuous only because it rears itself in clusters on a level with one's eyes, lacking beauty, perfume, and all that makes a blossom charming to the human mind - why has it been elevated by the botanists to the dignity of lending its name to a large and important family, and why is it mentioned at all in a popular flower book beside the more showy ornaments of nature's garden? Both questions have the same answer: Because it is the typical flower of the family, and therefore serves as an illustration of the manner in which many others are fertilized. Beautiful blossoms are by no means always the most important ones.
It well repays one to observe the relative times of maturing anthers and stigmas in the flowers, as thereby hangs a tale in which some insect plays an interesting role. The figwort matures its stigma at the lip of the style before its anthers have ripened their pollen. Why? By having the stigma of a newly opened flower thrust forward to the mouth of the corolla, an insect alighting on the lip, which forms his only convenient landing place, must brush against it and leave upon it some pollen brought from an older flower, whose anthers are already matured. At this early stage of the flower's development its stamens lie curved over in the tube of the corolla; but presently, as the already fertilized style begins to wither, and its stigma is dry and no longer receptive to pollen, then, since there can be no longer any fear of self-pollination - the horror of so many flowers - the figwort uncurls and elevates its stamens. The insect visitor in search of nectar must get dusted with pollen from the late maturing anthers now ready for him. By this ingenious method the flower becomes cross-fertilized and wastes the least pollen.
Bees and wasps evidently pursue opposite routes in going to work, the former beginning at the bottom of a spike or raceme, where the older, more mature flowers are, and working upward; the wasps commencing at the top, among the newly opened ones. In spite of the fact that we usually see hive bees about this plant, pilfering the generous supply of nectar in each tiny cup, it is undoubtedly the wasp that is the flower's truest benefactor, since he carries pollen from the older blossoms of the last raceme visited to the projecting stigmas of the newly opened flowers at the top of the next cluster. Manifestly no flower, even though it were especially adapted to wasps, as this one is, could exclude bees. About one-third of all its visitors are wasps.