The flower story of the sage is so peculiar that Darwin has used it to illustrate the mechanisms present in some flowers which the visiting insects must work in order to get the nectar. The scarlet sage, which gladdens our flower beds during the summer and autumn with its brilliance, has as interesting a story as has any of its family. Looking at it from the outside, we should say that its nectar-wells lie too deep to be reached by any insect except a moth or butterfly, or a humming bird; there is no platform for a bee to alight upon, and the tube is too long to be fathomed by a bee's tongue; but the bees are very good business folk; they adapt themselves to flowers that are not adapted to them, and in autumn the glow of the salvia attracts the eye scarcely more than the hum of the visiting bees attracts the ear.
The salvia, or scarlet sage, showing the bracts still present above and falling as the flowers open.
The calyx of the salvia is as red as the corolla, and is somewhat fuzzy while the corolla is smooth. The calyx is a three-lobed bulging tube held stiff by rather strong veins; there is one large lobe above and two small ones below the corolla. The corolla is a tube which is more than twice the length of the calyx; it is prolonged above into a projecting hood, which holds the anthers and the stigma; it has a short, cuplike lower lip and two little turned-back, earlike lobes at the side.
The special mechanism of the salvia is shown in the stamens; there are two of these lying flat along the floor of the corolla-tube and grown fast to it. Near the mouth of the tube, each of these lifts up at a broad angle to the roof, and is more or less T-shaped; at the tip of one of the arms of the T is an anther while the other arm is longer and slants down and inward to the floor of the tube, as shown at 2 in the figure.
1. Blossom of scarlet sage as seen from outside.
2. The same flower with side removed showing the arrangement of its parts.
3. A bee working the stamen's mechanism as she seeks the nectar.
The bee visiting the flower and entering the corolla-tube, pushes her head against the inner arms of the stamens, lifting them, and in so doing causes the anthers on the front arms of the T to lower and leave streaks of pollen along her fuzzy sides. The stigma is at first concealed in the hood; but, when ripe, it projects and hangs down in front of the opening of the corolla-tube, where it may be brushed along one side or the other by the visiting insect, which has been dusted with the pollen of some other flower. The stigma-lobes open in such a manner that they do not catch the pollen from the insect backing out of their own corolla. As the nectar is at the base of the corolla-tube, the bees, in order to get it, crawl in almost out of sight. Late in the season they seem to "go crazy" when gathering this nectar; I have often seen them searching the bases of the corolla-tubes which have fallen to the ground, in order to get what is left of the sweet treasure.
But the pollen story is not all that is of interest in the salvia. Some of the parts of the flower which are green in most blossoms, are scarlet as a cardinal's robe in this. If we glance at a flower stalk, we see that at its tip it looks like a braided, flattened cone; this appearance is caused by the scarlet, long-pointed bracts, each of which covers, with its bulging base, the scarlet calyx which in turn enfolds the scarlet flower bud. These bracts fall as the flowers are ready to open, making a brilliant carpet about the plant. Each flower stem continues to develop buds at its tip for a long season; and this, taken together with its scarlet bracts and flowers, renders the salvia a thing of beauty in our gardens, and makes it cry aloud to pollen-carriers that here, even in late autumn, there is plenty of nectar.
Leading thought—This flower has the bracts and calyx scarlet instead of green, and this makes it a brilliant mass of color to please our eyes and attract the pollen-carrying insects. Its anthers are arranged at the tip of two levers, which the insects push up and down as they enter the flower, thus becoming dusted with pollen.
Method—The structure of this flower may be studied in the schoolroom and its mechanism there understood; but the most important part of the lesson is the observation out-of-doors upon the way the bees work the stamen levers when seeking the nectar. This is best observed during late September or October, after other flowers are mostly gone, and when the bees are working with frantic haste to get all the honey possible.
1. How does the calyx of the salvia differ from that of other flowers in color? How does it differ from the corolla in texture? How many lobes has it? How are they placed about the corolla?
2. What is the shape of the corolla? How does it make a hood over the entrance to the tube? What does the hood hold? Is there any platform made by the lower lip of the corolla for a visiting insect to alight upon?
3. Cut open one side of the corolla and describe how the stamens are arranged. Thrust your pencil into an uninjured flower and see if the anthers in the hood are moved by it. How? Describe how a bee in visiting this flower moves the anthers so as to become dusted with pollen.
4. Where is the stigma? How does it receive pollen from visiting insects? Would it be likely to get the pollen which has just been scraped off from its own anthers by the bee? Why?
5. Experiment to find where the nectar is. Do you ever see bees getting the nectar from fallen flowers? Do they get it from the "front" or the "back door?"
6. What other parts of this flower are red, which in other flowers are green? How does this make the budding portions of the flower stem look? Why does this make the salvia a more beautiful plant for our gardens?
7. Compare the mechanism of the stamens of the scarlet sage with the mechanism of the stamens of the common garden sage.