This section is from the book "The Native Flowers And Ferns Of The United States ", by Thomas Meehan. Also available from Amazon: The Native Flowers and Ferns of the United States in Their Botanical, Horticultural, And Popular Aspects.
Rough-bristly throughout; stem stout (three to six feet high), leafy to the top; leaves pinnately parted, petioled, but dilated and clasping at the base; their divisions lanceolate or linear, acute, cut-lobed or pinnatifid, rarely entire; heads few (one to two inches broad), somewhat racemed; scales of the involucre acute, tapering into long and rigid points; achenia broadly winged and deeply notched. (Gray's Manual of the Botany of the Northern United States, See also Chapman's Flora of the Southern United States, and Wood's Class-Book of Botany.)
THE species now illustrated is a very strong growing" plant, often reaching a height of six feet. To get it within the limits of our plate, sections of its most characteristic portions have had to be made, but these are quite sufficient to enable the student to recognize the plant. This is, of course, satisfactory to the botanist, but will scarcely enable the lover of beauty to form an idea of the character of the plant. As it appears in the illustration it is coarse and heavy, and in a lesson in aesthetics might do perhaps to teach the student what to avoid. But it is for all this a plant well worthy of our acquaintance, for its botanical name carries us back a long way into ancient history, while there is so much of its own to attract attention, that it is doubtful whether any plant would do more honor to the selection we have to make amonog the "Native Flowers and Ferns" for our work.
Silphion is the name applied by Dioscorides, the ancient Greek physician, to a gum-bearing plant, or rather plants; for Bauhin tells us there were two kinds - " the asa-fcetida and the asa-dulcis." The juice of the plant was called laser, and hence we have laserpitium by the Latins, representing the same plant. Modern botanists identify this offensive-smelling gum, the asafoetida, with Ferula Asafoetida of the East; and the Sweet "asa," or asa-dulcis, with Thapsia garganica, plants of the Parsley family. The ancient Greeks attributed almost miraculous virtues to these drugs. They were believed to be able to give sight to the blind, and to make old people young again. So famous were they that the physicians from the Libyan country where it grew were widely esteemed, and the princes of Cyrene had a representation of the plant on the reverse of their coins. The drug itself was so precious that it was sold by its weight in gold, from which circumstance it probably derives its name - asa being a Greek name for a certain weight or pound - and the two names might be rendered almost literally the "sweet" and the "bitter pound."
When Botany was reorganized by Linnaeus, he gave the name of Silphium to these plants, it being suggested probably by their odor, which has some resemblance to asafoetida; and it is remarkable that the species now illustrated is said to have powers, though unknown to him, but little, if any, inferior to the drug with which it had but a nominal relationship. A Nebraska correspondent of the Department of Agriculture in 1866 says that growing among the prairie grass, it possesses great medical properties. "Horses fed upon hay, with the polar plant intermixed, are never known to have the heaves. Cattle, sheep, mules and horses, are extremely fond of the heads of the plant while green, as well as when mixed with hay. The pure white resinous gum which they contain performs radical cures in all bronchial cases." The large fleshy roots are a favorite article of food with all the rodents that inhabit the country where the plant grows.
But it is rather in the life-history of the plant than in its family history, or from its medical and economical uses, that its chief interest is centred. It is known as the Polar or Compass plant, because its younger leaves turn their edges north and south, with the flat surfaces necessarily east and west. When the leaves become heavy, or are blown about by the wind, the north and south direction, though rarely wholly lost, is not so apparent; and this accounts for the doubts of those who have not had the opportunity of watching the growth from its earlier start in spring. In these latter cases the polarity is incontestable. How long this curious fact has been known is not clear. Dr. C. C. Parry, in the Botany of Owen's Geological Survey of Minnesota, published in 1852, refers to it as the "Compass" plant; but whether because this was the name in general use, or because the peculiarities of the plant had been brought to the attention of science a few years before, does not appear. The poet Longfellow, in "Evangeline," issued in 1847, referred to the popular notion, and General Alvord seems to have been the first to attract scientific attention to the plant in 1848. Longfellow's lines are well known. Evangeline is almost in despair at the long absence of her lover, and " ' Patience !' the priest would say; " have faith, and thy prayer will be answered; Look at this delicate plant that lifts its head from the meadow; See how its leaves are turned to the north, as true as the magnet - This is the compass-flower, that the finger of God has planted Here in the houseless wild, to direct the traveller's journey Over the sea-like, pathless, limitless waste of the desert. Such in the soul of man is faith. The blossoms of passion, Gay and luxuriant flowers, are brighter and fuller of fragrance; But they beguile us and lead us astray, and their odor is deadly. Only this humble plant can guide us here, and hereafter Crown us with asphodel flowers, that are wet with the dews of nepenthe.' "
The reason for this turning of the edge of the leaves to the north and the south has not been satisfactorily determined. Dr. Engelmann, in a paper read before the "American Association for the Advancement of Science," at St. Louis, in 1878, noted that the leaves had stomata on both sides. Plants in general have stomata only on the under surface, and this is taken to mean that stomata do not like light. From this Dr. Engelmann suggested that as the compass plant has these on both sides, there was an evenly balanced struggle to avoid the light, which would necessarily result in the edge of the leaf being towards the point of greatest light, that is, the meridian. There may be something wrong with this light-abhorring theory; at least, we have only room here to say that many vertical-leaved plants have the stomata on both surfaces, but show no polarity.
In the "Proceedings of the Academy of Natural Sciences of Philadelphia" for 1870, are some detailed facts about the growth of the flowers in the compass plant, which show that growth or the development of a plant is not one continuous process, but proceeds by jerks, rhythms, or waves of varying intensities. The large yellow ray petals close over the disc at night, commencing to expand at 4 in the morning, and becoming horizontal at 6.20. At 4. 40 five of the fifteen spiral coils composing the disc commence to grow. The tubular corollas complete their growth by 5.20. The stamens and false pistil keep growing till 5.45, when the stamens stop - the pistil going on till 6.10. By 9 in the morning bees arrived, and the florets (which are barren) fell under the touch of the insect, and in their fall fertilized the pistils in the ray florets, which are the only flowers yielding seed.
Its introduction to the notice of European botanists was probably through John Bartram. A letter of Collinson's to him, dated December, 1763, says: "I can tell thee Gordon has raised the fine, stately, broad-leaved Silphium; but thee mentions three fine species from New Virginia, by the Ohio; but which of them ours is I don't know; but thy specimens will set us right." And Linnaeus, in the second edition of his "Species Plantarum," published in the same year, says he derived his knowledge of the plant from Collinson, who had it "from Mississippi."
1. Barren male or disc flower.
2. Scale or involucel from the base of a disc floret.
3. A hair from the stem magnified.
4. Flower longitudinally-divided, showing (a) the receptacle, (b) the involucral scales, (c) the fertile ray floret with akene and deeply divided pistil, (d) ray floret from a side view, and (e) barren disc floret.
5. Portion of stem, showing leaf and its insertion.
6. Upper portion of a flowering stem. The whole from an Illinois specimen.