Abstracts of Papers - Harvard Forest - Harvard University

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plant communities that has been extensively employed throughout Europe. Basic principles by which different hierarchial groups of lichens are distinguished, are discussed and examples are given. Epiphytic lichen associ- ations have clearly been modified over the past two hundred years. This can be docu- mented by herbarium records as well as carto- graphic studies. Even the formerly widely distributed Xanthorion parietinae alliance, that normally prospers in areas adjacent hu- man settlements, has declined markedly. Many of the patterns in lichen community modifica- tions can be correlated with measured SO2 levels. A number of lichen species have ap- parently disappeared entirely from the Feder- al Republic of Germany and about 50% of the lichen flora is considered endangered. Poster Session BASILE, DOMINICK V., MARGARET R. BASILE and ROSS E. KONING. Lehman College of CUNY, Bronx, N.Y. 10468 and Rutgers Univ. Piscataway, N.J. 08854. - Ethylene production and its possible role in regulating leaf and branch development in Plagiochila arctica, a leafy liverwort. Ethylene production by gametophytes of Plagiochila arctica Bryhn & Kaal. in axenic culture was determined by means of gas- liquid chromatography (GLC). Exogenous indole acetic acid (IAA) at approx. 6x 10-5M markedly stimulated ethylene synthesis while aminoethoxyvinyl glycine (AVG) at approx. 10-5M significantly suppressed it. In these respects ethylene production and its regulation are the same in P. arctica as in representatives of the flowering plants (Magnoliophyta). Although these results may have been inferred, they were hitherto unsubstantiated. Furthermore, these data in conjunction with those ob- tained in previously completed experiments lend support to an hypothesis that auxin- induced ethylene synthesis plays an important role in regulating leaf and branch development in leafy liverworts, particularly those originating from ventral mero- phytes. JANSSENS, JAN A. & PAUL H. GLASER. Limnological Research Center, University of Minnesota, Minneapolis, MN 55455. - Fossil bryophytes and peat stratigraphy in the development of Red Lake Peatland, northern Minnesota. Ten peat cores, reaching down to the mineral sediment, taken along a transect 7-km long in the center of the vast Red Lake Peatland in northern Minnesota, were analyzed to reconstruct the development of a mire complex consisting of forested ovoid bog islands separated by internal water tracks marked by patterned fens. The reconstruction of past bog, poor-fen, and rich-fen communities is based primarily on the quantitative analysis of fossil bryophyte assemblag- Bryological and Lichenological Section 3 es; concentration by weight and volume, accumulation rates, and percentages of identified taxa were calculated. The sharply defined bryophyte zones were stratigraphically correlated among cores by radiocarbon dates, the regional pollen zonation, and bu- ried wood layers. Peat-accumulation rates, calculated from radiocarbon dates, were correlated with measure- ments of bulk density, humification, and peat ontoge- ny as based on the local paleoenvironmental reconstruction. The peat stratigraphy indicates that bog vegetation originated about 5000 years ago at the watershed crest and then extended downslope, growing over rich-fen peat in the process. Cores from the internal water tracks contain a striking sequence in fossil assemblages, changing from a basal rich-fen zone to a bog or oligotrophic poor-fen zone and then reverting back to a rich-fen zone towards the top. This stratigraphy supports an earlier hypothesis, based on the study of present-day landforms, that the internal water tracks originated recently within a continuous complex of forested raised bogs, with poor-fen lawn flanks. Conversion of the bog into ovoid islands resulted in the complex landscape. Contributed Papers Allen, Bruce H. Department of Biological Sciences, University of Cincinnati, Cincinnati, Oh 45221.- The protonema of Drummondia prorepens. Spore germination in D. prorepens is precocious and endosporic. On sowing of these endosporic protonemata dimorphic protonemal filaments arise: those with long rhomboidal cells having end walls oblique to the long axis, and those with cells more or less square the end walls at right angles to the long axia. By means of anticlinal and periclinal divisions in the latter a massive three-dimensional protonema is formed.. Periclinal divisions in the former results in their elongation into the medium. Occasional divisions at right angles to the oblique end walls of the long celled filaments form cells that give rise to three- dimensional cell masses. Leafy gametophytes originate on the primary cell mass within 20 days, and on the secondary cell masses within 59 days. This sporeling type is similar to that reported for some species of Ptychomitrium, Hedia and Drummondia. The sa.lient feature of this type is the ability to form, free from the constraint of the spore wall, a primary three- dimen- sional protonema. Rapid development of leafy gametophytes is considered the principal advantage of this type of sporeling development: minimizing the risk of dessication and of being washed onto an unsuitable substrate. ANDERSON, DAVID C., LARRY ST. CLAIR 360 Wakara Way Salt Lake City, Utah 84108 -Selection of useful parameters in assessing lichens as biological monitors of air pollution. The use of lichens as biological monitors of air quality although in its infancy affords an "early warning"
4 Bryological and Lichenological Section system to potential impacts of air pollution on biological activity. Two studies recently conducted in southeastern Wyoming and in eastern Utah evaluated the use of such a system. At permanent plots established at incremental distances from pollution sources the lichen community was characterized and the membrane permeability, a measurement of cell damage, of selected lichen speices was determined. The purpose of the studies was to identify paramenters most accurately replicated and to characterize the existing lichen community. In southeastern Wyoming, membrane- leakage values for Parmelia chlorochroa, a terricolous lichen, was significantly higher at the Dave Johnston plant, a plant on line since 1958, in comparison to the Laramie River plant, in use since 1980. Data from the Dave Johnston plant show significantly higher membrane leakage values, higher lichen selenium content and lower weight per individual at sites nearest the pollution source. On oil shale lands in eastern Utah, the results of a similar study showed that the percent- age of total lichen cover, the number of species/quad- rat and the sulfur content of the lichen thallus were the least variable parameters measured. The percent- age of total cryptogamic cover, the number of lichen species per unit area, membrane leakage and to some extent, elemental analyses of lichen tissue were parameters most replicatable and would, therefore, serve as good indicators of lichen community conditions. BENNETT, JAMES P. National Park Service, Air Quality Division, Box 25287, Denver, CO 80225. - Air pollution studies on lichens in Denver, Colorado. Denver, Colorado is not known for having very high air quality. The notorious "brown cloud" is easily observed by many visitors. Using the Pollutant Standards Index (PSI) for 1978 to 1980, Denver ranked fourth in the nation for having polluted air. The composition of the pollution is the subject of a continuing controversy, but the presence of S02 can not be ruled out. Know- ing that lichens are extremely sensitive to low levels of S02, a study was initiated to map lichen frequency on tree trunks. The presence/ absence of lichens are noted on a minimum of 100 trees at least 30 cm diameter in size in parks, cemeteries, school yards or other locations con- taining sufficient number of trees. To date, over 2500 trees have been sampled. Only two species of corticolous lichens are encountered in Denver, the most common being Xanthoria fallax. With over 20 sites sampled so far, a strong relationship has been found between the probability of encountering a lichen on a tree trunk and linear distance from the city center (r = 0.73). An objective of the study is to sample a minimum of 50 sites systematically located at selected distances and compass directions from the city center. A model can then be developed relating the probability of lichens occuring on tree trunks to various geographic parameters. With only one S02 monitoring station in Denver it will not be possible to relate these effects to air quality, but the observed trend would suggest the need for more monitoring. DALE , MARK R. T. Botany Dept ., University of Alberta, Edmonton, Alberta . T6G 2E 1 The geometry of adj oining lichen thalli in relation to their growth rates Models of the growth rates of lichen thalli usually include an initial phase of exponen- tial radial growth, followed by a phase of linear growth. These models predict that the shape of "truce" boundaries between adjoining thalli will have characteristic changes in curvature at points where growth has become linear. Thus a comparison of the shapes predicted from these models with those observed in boundaries between lichen thalli (most easily seen in species like those of Rhizocarpon which have distinct hypothalline margins) permits an evaluation of the models without long term studies. In cases where the models prove to be appropri- ate, the geometry of the boundaries provides estimates of the size at which growth be- comes linear. It is possible that once the growth curves for several species are known, a comparison of inter- and intraspecific boundaries will prove useful in evaluating the relative rates of linear growth in different species. DEWEY, RICHARD M. Department of Biology, Texas A&M University, College Station, TX 77843 - Electrophoretic evidence for the recognition of Riccia mcallisteri. The relationship of the two concepts, Riccia dictyospora M.A. Howe, Bull. Torrey Bot. Club 28:163. 1910., and R. mcallisteri M.A. Howe, The Bryologist 20:35. 1917., is among the most vexing problems in the taxonomy of North American representatives of Riccia subgenus Riccia. An inability to discern reliable critical morphological differences between the two species has prompted some workers to view R. mcallisteri as a taxonomic synonym. Plants repre- senting R. dictyospora, sensu lato, have been collected in several central Texas localities, including the type locality of R. mcallisteri. When surveyed with starch-gel electrophoresis, plants assignable by morphology to either R. dictyospora or R. mcallisteri have exhibited distinctive phenotypes for isozymes of malate dehydrogenase, acid phospha- tase, peroxidase and aspartate amino transf erase. This preliminary electrophoretic evidence supports the recognition of R. dictyospora and R. mcallisteri as distinct species. ELIX, JOHN A. Department of Chemistry, Australian National University, P.O. Box 4, Canberra 2600, Australia. - Lichens in Papua New Guinea The lichen flora of Papua New Guinea is still poorly known, but even after a cursory investigation the contrast between the flora of the tropical lowland forests and higher altitude montane forests are particularly striking. Corticolous substrates are most important in both environments, but crustose growth forms growing on tree trunks and branches dominate in the coastal forests where lichen cover is high but biomass low. Genera such as Graphis, Arthonia and Anthracothecium are particularly abundant In the lower montane Castanopsis and Araucaria forests pantropical macrolichen genera such as Parmotrema, Usnea and Leptogium are prominent, while in the higher montane Nothofagus forests the genera Pseudocyphellaria, Sticta, Lobaria and Anzia are preponderant. Interestingly the former two genera and common associates (Menegazzia, Psoroma) are presumably of Gondwanaland origin and also prominent in the Nothof agus f orests of Tasmania, New Zealand and Chile, while Lobaria and Anzia appear of Asiatic origin. This dichotomous origin appears to be reflected in much of PNG's lichen flora.
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