| BEN |
| BOTANICAL ELECTRONIC NEWS |
|---|
| ISSN 1188-603X |
No. 121 December 9, 1995
Uncertainty reigned until 1794 when John Lindsay, a British surgeon, showed that ferns reproduced from their dust. He discovered this while stationed in Jamaica, where he noticed hundreds of young ferns arising on freshly exposed soil after rains. With a microscope, he searched the soil in the hope of finding a fern seed, but was unsuccessful. Undaunted, he decided to sow some of the dust-which he suspected as the true fern seed-and keep it in his room for observation.
Lindsay gathered the dust from several weedy ferns and sprinkled it over soil in a flower pot. He placed the pot in a window of his room, watered it daily, and every day or two examined a small portion of the soil with his microscope. Here he describes what happened.
"I could always readily distinguish the dust or seeds from the mould, but observed no alteration till about the 12th day after sowing, when many of the small seeds had put on a greenish colour, and some were pushing out their little germ, like a small protuberance, the rudiment of the new fern. This little protuberance gradually enlarged. They had acquired small roots, and the remains of the little seeds were still discernible where the roots of the infant plant commenced. Although the young ferns were now very conspicuous by the microscope, the naked eye could see nothing but a green appearance on the surface of the mould, as if it were covered with some very small moss: this was the numberless young plants from the quantity of the seed sown. In some weeks this moss began to appear to the naked eye like small scales which gradually enlarged: they were generally of a roundish figure, somewhat bilobate, but sometimes more irregular; they were of a membranous substance, like some of the small lichens or liverworts, for which they might readily be mistaken, and of a dark green colour. At last there arises from this membrane a small leaf, different from it in colour and appearance, and shortly after another still more different. Now each succeeding leaf grows larger than the last, till they attain the full size, and are complete in all the parts and discriminating characters of their respective species."
Clearly, Lindsay thought he had seen a full-sized fern develop from a mote of fern dust. He therefore felt certain that the dust was the true fern seed.
A busy medical practice kept Lindsay from making further observations, until one day he received a letter from Sir Joseph Banks, president of the Royal Society of London and scientific advisor to the Royal Botanical Gardens, Kew. Banks asked Lindsay to collect Jamaican plants, especially ferns, and send them to England for cultivation. Lindsay wrote back that given the risk of transporting green ferns over such a great distance, he would send some of their seeds instead. Banks must have been flabbergasted that Lindsay claimed knowledge of the true fern seed. He wrote back that if Lindsay could furnish the means of making ferns grow from seed, he would be given the credit of having made a valuable discovery, one that he (Banks) would communicate to the Linnean Society of London.
Lindsay sent Banks the seeds along with instructions for their sowing. The result was pteridological history. Thanks to Lindsay's information, gardeners in England learned to propagate ferns from spores, and they passed this knowledge to colleagues in other countries. Ferns began to enrich greenhouses, gardens, and parks around the world. Furthermore, the horticulturists at Kew began raising ferns sent from far corners of the British Empire. They amassed the world's largest and most species-rich collection of living ferns-a distinction held to this day (the Kew collection is important scientifically as well as horticulturally). James Edward Smith, a pteridologist and one of England's leading botanists, commemorated Lindsay for his discovery by naming a genus of tropical ferns after him: Lindsaea.
Yet Lindsay's observations raised more questions. Were the
"membranes" or "scales" he observed equivalent to the seed leaf
or cotyledon of flowering plants? If the dust was equivalent to
the seed, where were the pollen-producing anthers? (The pollen,
of course, was necessary to "stimulate" the development of the
seed.) How and when did pollination take place? :.... conclusion
in BEN 122:
We discovered several "new" populations of Cimicifuga elata in the Elwha River valley during summer 1995. The plant was previously known to occur in the Elwha. At present, we know of 16 sites of 1-5 individuals along the Whiskey Bend Road in Olympic National Park. The plants are mostly in the road cut but a few are in the forest above. Additionally, a sizable population of nearly 300 individuals was discovered on the "Cascade Rock" nature trail above the Elwha Campground. Here, many plants are within 1 meter of the trail in the "trail cut" but many other individuals occur on the slopes above and below the trail. All these populations were mapped and permanent plots established for future monitoring. Our permanent plots were established so we could potentially test hypotheses concerning behaviour of the plants as "singles", "groups" (of 3 or more individuals within a 1 m2 area) as well as examining plant demography in the "undisturbed", "road cut", and "trail cut" situations. It looks to us like the plants may benefit considerably from the mineral soil exposed by the human disturbance. Most plots were in Douglas-fir/bigleaf maple stands on steep slopes (>> 35 degrees). We suspect that there needs to be some subsurface moisture available. Our results are in general agreement with those of Thomas N. Kaye (Oregon) who has prepared a summary of populations throughout western Oregon and in the Olympics.
Interestingly, clusters of individuals in the trail cut were
always below a larger, fruiting, individual above. It seemed
that the "parent" dropped seeds along the trail. Looking at
genetic links among clusters and populations should prove quite
fascinating.
In 1992 and 1993, the Plant Conservation Biology Program at the Oregon Department of Agriculture engaged in cooperative research with three Bureau of Land Management Districts and three National Forests in Oregon to evaluate the habitat of Cimicifuga elata and the effects of timber harvest on populations of the species. Our results are too lengthy to summarize here, but a few points may be of interest to readers of BEN. For example, for a rare species, C. elata is unusual in having a large geographic range (B.C. to southern Oregon) and widely scattered, usually small populations. Oddly, though, at the southern end of the species' range the populations tend to be quite large (over 1,000 individuals), possibly associated with cryptic taxonomic differences between northern and southern types (Ed Alverson, pers. comm.) or ecotypic differences.
After sampling populations throughout Oregon, and Washington to a lesser degree, we concluded that there were three primary habitat features common to most populations:
It is very gratifying to hear the results of studies in Olympic National Park that corroborate these findings. We also found many populations along road cuts and trails, and attributed this pattern to increased light availability and mineral soil for seedling establishment. I encourage Ed Schreiner to pursue studies of population genetics of this species--indeed, they could be very interesting.
Incidentally, timber harvest/canopy removal tends to result in rapid growth of individual plants and an increase in the proportion of reproductive plants in the population. Populations in undisturbed old-growth forest tend to have few or no reproductive plants. We believe the species' natural distribution is related to the formation of canopy gaps. Clear-cut timber harvest, however, may only result in a short-term burst of reproduction. Information from ten to thirty years after harvest is sadly lacking, and we suspect that C. elata could be 'choked out' of densely stocked forest stands. Instead, careful thinning of forest stands could be beneficial to the species.
Contact Tom Kaye (kayet@bcc.orst.edu) for copies of the
report: Oregon Department of Agriculture, 635 Capitol NE,
Salem, OR, 97310, USA.
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