This common flower of our gardens, sending up from a mass of dark, deeply-cut leaves tall racemes of purple or blue flowers, has a very interesting story to tell those who watch it day by day and get acquainted with it and its insect guests. The brilliant color of the flowers is due to the sepals, which are purple or blue, in varying shades; but as if to show that they are sepals instead of petals, each has on the back side near its tip, a green thickened spot. If we glance up the flower stalk, we can see that, in the upper buds, the sepals are green, but in the lower buds they begin to show the blue color; and in a bud just ready to open, we can see that the blue sepals are each tipped with a green knob, and this remains green after the sepals expand. The upper and rearmost sepal is prolonged into a spur, which forms the outside covering of the nectar-spur; it is greenish and wrinkled like a long-wristed, suede glove; two sepals spread wide at the sides and two more below. All this expanse of blue sepals is simply for a background for the petals, which, by their contrasting color, show the bees where to probe for nectar. Such inconsequential petals as they are! Two of them "hold hands" to make an arch over the entrance to the nectar tube; and just below these on each side are two more tiny, fuzzy, spreading petals, often notched at the tip and always hinged in a peculiar way about the upper petal; they stand guard at the door to the nectar storehouse. If we peel off the wrinkled sepal-covering of the spur, we can see the upper petals extending back into it, making a somewhat double-barreled nectary.
If we look into a larkspur flower just opened, we see below the petals a bunch of green anthers, hanging by white threadlike filaments to the center of the flower and looking like a bunch of lilliputian bananas. Behind these anthers is an undeveloped stigma, not visible as yet. After the flower has been open for a short time, three or four of the anthers rise up and stand within the lower petals; while in this position, their white pollen bursts from them, and no bee may then thrust her tongue into the nectar-spur without being powdered with pollen. As soon as the anthers have discharged their pollen, they shrivel and their places are taken by fresh ones. It may require two or three days for all the anthers to lift up and get rid of their pollen. After this has been accomplished, the three white, closely adhering pistils lift up their three stigmas in the self-same path to the nectar; and now they are ready to receive the pollen which the blundering bee brings from other flowers. Since we cannot always study the same flower for several consecutive days, we can read the whole story by studying the flowers freshly opened on the upper portion of the stalk, and those below them that are in more advanced stages.
The bees, especially the bumblebee, will tell the pollenation story to us in the garden. The contrasting color of the petals and sepals tells her where to alight; this she does accurately, and the inconsequential lower petals seem made for her to grasp; she presses them to her breast with her front and middle legs with a dramatic, almost ecstatic, gesture that is comical to witness, and holds them firmly while she thrusts her head into the opening between them; she probes the spur twice, evidently finding there the two nectar-wells. It is a fascinating pastime to follow her as she goes from flower to flower like a Madam Pompadour, powdered with her white pollen. In order that a bee may work on these flowers, it is necessary that they hang vertically. The tips of the tall flower stalks are likely to bend or curl over; but no matter what direction the broken or bent stem takes, the flowers will twist around on their pedicels until they face the world and the bee, exactly as if they were on a normally erect stem.
All the larkspurs have essentially the same pollen story, although some have only two petals; in every case the anthers at first hang down, and later rise up in the path to the nectar, in order to discharge their pollen; after they wither, the stigmas arise in a similar position.
The bee-larkspur has a very beautiful fruit. It consists of three graceful capsules rising from the same base and flaring out into pointed tips. The seeds are fastened to the curved side of each capsule, which, when ripe, opens so that they may be shaken out by the winds. When studying the bud, we notice two little bracts set at its base and these remain with the fruit.
Leading thought—The bee-larkspur begins blossoming early in the season, the blossom stalk elongating and developing new buds at its tip until late in autumn. The flower has a very interesting way of making the bees carry its pollen.
Method—Bring to the schoolroom a flower stalk of the bee-larkspur, and there study the structure and mechanism of the flower. This lesson should inspire the pupils to observe for themselves the visiting bees and the maturing seeds. Ask them to write an account of a bumblebee making morning calls on the larkspurs.
1. Which flowers of the larkspur open first—those near the tip of the stem or those below?
2. Examine the buds toward the tip of the flower stalk. What color are the sepals in these buds? Do the sepals change color as the flower opens? Note the little green knobs which tip the closed sepals that clasp the bud. What color are the sepals on the open flower? Is there any green upon them when open?
3. Where is the nectar-spur? Which sepal forms this? How are the other sepals arranged?
4. Now that we know the flower gets its brilliant color from its sepals, let us find the petals. Look straight into the flower, and note what forms the contrasting color of the heart of the flower; these are the petals. Can you see that two are joined above the opening into the nectar-tube? How many guard the entrance from below? How are these lower petals hinged about the upper one? Peel a sepal-cover from the nectar-spur, and see if the upper petals extend back within the spur, forming nectar-tubes?
5. Take a flower just opened, and describe what you see below the petals. What is the color of the anthers? Of the filaments? Can you see the stigma?
6. Take a flower farther down the stalk, which has therefore been open longer, and describe the position of the anthers in this. Are there any of them standing upright? Are they discharging their pollen? What color is the pollen? Are these upright anthers in the way of the bee, when she thrusts her tongue into the nectar-tube?
7. Take the oldest flower you can find. What has happened to the anthers? Can you see the pistils in this? In what position now are the stigmas?
8. Push aside the anthers in a freshly opened flower and see if you can find the stigmas. What is their position? How do they change in form and position after the pollen is shed? Do they arise in the path of the bee before all the pollen from the anthers of their own flower is shed? If so, how are they pollenated?
9. Suggestions for Observation in the Garden—Watch a bumblebee working on the larkspur and answer the following questions: How does she hold on to the flower? Where does she thrust her tongue? Can she get the nectar without brushing the pollen from the anthers which are lifting up at the opening of the nectar-tube? In probing the older flowers, how would she come in contact with the lifted stigmas? How do the petals contrast in color with the sepals? Does this tell the bees where to look for nectar? Compare the common larkspur with the bee-larkspur, and notice the likeness and difference. What kind of fruit capsules has the bee-larkspur? Describe the seeds, and how they are scattered.