|BOTANICAL ELECTRONIC NEWS|
No. 120 December 2, 1995
In Shakespeare's Henry IV, Falstaff, Prince Hal, and Poins scheme to rob a rich merchant on his way to London in the dark hours of the early morning. Because they need help with the heist, one of Falstaff's henchmen tries to persuade another thief to join them. He says to the thief: "We steal as in a castle, cock-sure; we have the receipt of fern-seed, we walk invisible." To which the thief replies, "Nay, by my faith, I think you are more beholding to the night than to fern-seed for your walking invisible" (Act 2, Scene 1, lines 95-98).
What do the thieves mean by fern seed? Anyone who has taken a botany course knows that ferns don't have seeds; instead, they disperse by tiny dustlike spores. Did people in Shakespeare's day believe that ferns had seeds? And what's this about walking invisible?
In 1597 when Henry IV was written and performed, the belief that ferns had seeds was common and widespread. To be sure, no one had ever seen a fern seed, but they couldn't imagine how ferns (or any plant, for that matter) could reproduce without such propagules. Therefore they reasoned that ferns must have seeds. "The views of those who believe all plants have seeds are founded on very reasonable conjectures," wrote Joseph Pitton de Tournefort, a celebrated French botanist, in 1694.
But sometimes the conjectures went too far. The early herbalists, for example, claimed that the fern seed had to be invisible because no one had ever seen it. Furthermore, they asserted that it conferred invisibility to the bearer; if you held the fern seed, you walked invisible. They also specified that the seed could only be collected at midnight on St. John's Eve (Midsummer's Night Eve, June 23), the exact moment it fell from the plant. You could catch it by stacking 12 pewter plates beneath a fern leaf; the seed would fall through the first 11 plates and be stopped by the 12th. If you came up empty-handed, it was because goblins and fairies, which were allowed to roam freely that one night of the year, had snatched the seed as it fell.
Of course, not everyone believed all this about invisibility, but they did believe that ferns had seeds. The only problem was, what was the fern seed? Many early botanists suspected it was the dust liberated from the dark spots or lines (the sori) on the underside of the fern leaf. Other botanists thought that this dust was not seed, but instead equivalent to pollen that impregnated a female organ somewhere on the plant.
The first person to scientifically investigate fern dust was Marcello Malpighi, the famous Italian anatomist. In the late 1600s, he focused his microscope on the curious, dark spots or lines on the undersides of fern leaves. These resolved into hundreds of tiny "globes" or "orbs" (the sporangia), each encircled by a thick, segmented band (the annulus). Inside the orbs sat the dust, which appeared as round or bean-shaped bodies. He noted that the dust was hurled out of the orb by the catapultlike action of the annulus. Nearly half a century later, Malpighi's observations were confirmed and elaborated by Nemiah Grew, an English microscopist. But the observations of neither man solved whether the dust was equivalent to pollen or seed.
Even the great Swedish botanist Carl Linnaeus, the Father of
Botany, was puzzled about the nature of fern dust. In a letter
written in 1737 to fellow Swedish botanist Albrecht von Haller,
he said that "this powder seen under a microscope, exactly
agrees with the dust of the anthers in other plants." But one
month later he said ":I know: nothing about the imperfect tribes
of plants :mosses and ferns: and must confess my ignorance
whether what I see is seed, or dust of the anthers." In 1751,
however, he changed his mind and asserted that the dust was the
true fern seed. Despite his flip-flopping, Linneaus was sure
about one thing: ferns had seeds. :... continuing in BEN 121:
Abstract. A predictive model for bryophyte distribution, water table position, and seasonal mean methane (CH4 ) emission was developed for two areas of northern peatland: the Clay Belt of Ontario and the Labrador Trough of Quebec. Water table position and CH4 flux were the most important environmental variables in canonical correspondence analyses (CCA) of bryophyte data. Water chemistry constituted a second environmental gradient, independent of hydrology and CH4 flux.
Weighted averaging regression and calibration were used to develop a model for predicting log CH4 flux from bryophyte distribution. The model showed an increase in log CH4 flux from hummock to carpet and pool species, corresponding with a decrease in height above the mean water table position. The exceptions were rich-fen pool species, which had low CH4 flux optima in spite of their moisture status. Tolerances were greatest for mid-hummock and least for carpet and pool species. No overlap in tolerances occurred between hummock and pool species, suggesting that species at either end of the height gradient are the best predictors of CH4 flux.
Error analyses showed that bryophytes are equally as effective
as water table position for predicting mean CH4 flux even though
bryophytes are only surrogates for the degree of
anaerobism/aerobism in the peat profile. Bryophytes are distributed in well-defined zones along microtopographic gradients;
they integrate long-term changes in the water table, which
fluctuates on a daily and seasonal basis along with CH4 flux,
and may be more easily mapped with remote-sensing techniques.
Bryophytes, however, are only useful for predicting CH4 flux
within a region; similar species values cannot be extrapolated
to other northern peatlands where different climatic and
biogeochemical factors may result in different ranges of CH4
emission. The model may be used in palaeoreconstructions of
methane emission and for biological monitoring of climate
The CA Exotic pest Plant Council, OR Dept. of Ag, the Pacific Northwest Exotic Pest Plant Council, and the WA State Weed Board are jointly sponsoring a broom symposium (includes Scot's, French, Spanish, and Portuguese brooms). The symposium will be held 16-18 April 1996 at Portland State University, Portland, Oregon, USA. Symposium focuses on biology, ecology, and management of brooms.
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