The construction of the flower of milkweed is so singular that it should be described. Without the magnifying-glass one sees 5 short, pointed sepals hidden under 5 larger petals turned backward and downward. The next row of bodies standing up over the flower-center may be taken for stamens. But through the glass we see that these are tubular bodies, colored like petals, containing a curved, needle-like hook. The latter is called a horn; the tube inclosing it, a hood. All 5 of the horns lie protectingly over the stamens and pistil. Pull off the hoods, with their inclosed horns, and see what strange things the stamens are.
The filaments of the stamens, united into a tube, stand around the pistil. The long cells of the anthers open lengthwise, often in bud. The pollen, instead of being in grains, is in a long, yellow, flat mass, one in each cell (in shape like an apple seed), which can be squeezed out entire with thumb and finger. Two of these, from different, adjacent anthers, cling together by a thread, and adhere to insects visiting them and so are carried to other flowers.
There are seemingly two pistils (really two ovaries) united above into a large, flattish, sticky stigma which catches and holds the pollen-masses borne to it by bees. In the flower the pollen-masses lie too low for its own stigma. The insect visit is absolutely necessary for fertilization. Now perhaps we have found a use for the hoods. They probably collect and store nectar, and so invite the insects, upon whose help the flower is dependent. The reflexed corolla could not hold any nectar, and without nectar bees would pass the milkweed by.
The Mint Family is large and important. The general characteristics of the Family are square stems, opposite or whorled leaves, a fragrance given out by numerous oily glands, and a fruit of four achene-like nutlets, 1 in each of 4 visibly distinct divisions of the ovary, from the center of which arises the style. The corolla is a tube with 2 lips, each lip, or sometimes the upper one only, divided into lobes. A square-stemmed, herbaceous plant, with the well-known minty odor and the 4-lobed ovary, is quickly relegated to this Family.
Many of the housekeeper's best flavorings - lavender, marjoram, thyme, sage, rosemary - belong here, as well as the horehound, catnip, pennyroyal, and peppermint which used to hang drying in our grandmothers' attics, the most prized belongings of the home pharmacy. Whether the drugs which have superseded these simple herb drinks are, on the whole, more conducive to long life is a question for life-insurance companies to consider.