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. And as all the flowers on any one plant are of the same kind, we have here a marvelous mechanism to secure cross-fertilization. His experiments with this loosestrife also demonstrated that "reproductive organs, when of different length, behave to one another like different species of the same genus in regard both to direct productiveness and the character of the offspring; and that consequently mutual barrenness, which was once thought conclusive proof of difference of species, is worthless as such, and the last barrier that was raised between species and varieties is broken down." (Muller.) Naturally the bright-hued, hospitable flower, which secretes abundant nectar at the base of its tube, attracts many insects, among others, bees of larger and middle size, and the butterflies for which it is especially adapted. They alight on the stamens and pistil on the upper side of the flower. Those with the longest tongues stand on one blossom to sip from the next one: this is the butterfly's customary attitude. But nearly every visitor comes in contact with at least one set of organs. When Darwin first interpreted the trimorphism of the loosestrife, we can realize something of the enthusiasm such a man must have felt in writing to Gray: "I am almost stark, staring mad over lythrum.... For the love of Heaven have a look at some of your species, and if you can get me some seed, do!" Long ago this beautiful plant reached our shores from Europe, and year by year is extending its triumphal march westward, brightening its course of empire through low meadows and marshes with torches that lengthen even as they glow. It is not a spring flower, even in England; and so when Shakespeare, whose knowledge of floral nature was second only to that of human nature, wrote of Ophelia, "With fantastic garlands did she come, Of crow-flowers, nettles, daisies, and long purples,"