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Botanical history has recorded significant contributions of bryology to its conceptual development and to man’s scientific knowledge. The discovery of sexual chromosomes in plants by Allen and the production of the first polyploids by Wettstein are but two scientific achievments in which bryophytes had an outstanding role. Currently, their use in environmental monitoring and the identification of active principles, make bryophytes objects of great pragmatic interest.
214 Lichen and 38 bryophyte species are reported from Cerro Guaiquinima, a sandstone table mountain in southeastern Venezuela, thus fas almost unexplored for these groups and apparently undisturbed by man. Slightly over half of these species have also been reported from the north slope of Mount Roraima and surroundings, a nearby area with similar edaphic and climatological conditions.
The pleurocarpous moss genus Isopterygium (Hypnaceae) is revised for Latin America. Although as many as 92 species and varieties have been reported for the region over past years, these are currently accommodated by the present revision into only eight species. The most common taxon throughout most of Latin America, Isopterygium tenerum (Sw.) Mitt, is also the most polymorphic and presently 45 taxa are recognized as synonyms. The other seven species are I. affusum Mitt., I. acutifolium Irel., I. byssobolax Par., I. jamaicense Buck Broth., I. subglobosum Herz., and I. tenerifolium Mitt.+
References are made to cytotoxic and/or antitumor compounds that have been isolated - ansamitocin P-3 from Claopodium crispifolium (Hook.) Ren. & Card. and Anomodon attenuatus Hueb., or an associated actinomycete, and ohioensins and pallidisetums from Polytrichum spp. Several hundred collections, which have been obtained from temperate regions of North America during 1990 and 1991, are currently being screened in new bioassays; active sesquiterpene lactones have been recently isolated from species of Porella. The methodologies of collecting and screening bryophyte samples are discussed with consideration to costs based on expected number of samples that might be collected in a day, the diversity in the collections as related to phytogeography and vegetation types, and the bryophyte cover that is vanishing in many forest regions of the United States. The difficulties in obtaining large collections for isolation of active agents are also discussed by examplerecollection of Claopodium crispifolium.
Phenological observations and sex ratios in Marchantia chenopoda L. (Hepaticae: Marchantiaceae)
(1992)
Sex ratios were determined for 15 populations of Marchantia chenopoda L. along Puerto Rico. Sex was determined for twenty randomly selected individuals from each population. A female bias was observed in most populations. A census of reproductive structures of M. chenopoda was performed every two weeks in order to determine phenology. The highest archegoniophore count was observed to occur in January and February; minimum and maximum fertilization distances were 0.7 cm and 65 cm, respectively. Young sporophytes were most frequently observed at the beginning of the rainy season, in April and May. The highest frequency of mature sporophytes occurred during the dry season, in January and February. Capsules opened mostly during the heavy rainy season, from August to November. Protonemata were observed in the periphery of the population. Most young sporophytes aborted at the end of the moderate to heavy rainy season, from June to August. Immature gemmae cups were most frequent at the beginning of the rainy season, in April and May. Mature gemmae cups were observed throughout the rainy season, but were most frequent in September.
Tropical deforestation, inevitably, leads to the local loss of bryophyte species. Recent studies show that the degree of species loss may vary considerably and depends on the scale or amount of habitat change that has occurred. Predictably, the shade epiphytes are most seriously affected by disturbance. An estimated 10% of the bryophyte species of neotropical rain forests are under threat. Based on data from recent monographs, a first list of 19 endangered and 27 rare species of these forests is presented. Critical areas for threatened species include Costa Rica and Panama, the Greater Antilles, the Chocó, southeastern Brazil, and parts of Amazonia. Protection of as much as possible of the remaining natural rain forest area seems the best approach to the conservation of the tropical bryophyte flora.
The Index of Atmospheric Purity (IAP) was used to make a preliminary evaluation of epiphytic moss response to atmospheric pollution in the urban area of Mexico City. Areal analysis indicates that there is a significant negative correlation (p < 0.5) between IAP values and SO2, NO2, NOx, Pb and temperature values of -0.45, -0.90, -0.80, -0.80, -0.90. Significant positive correlation (p < 0.05) between IAP values and O3, rainfall and relative atmospheric humidity with values of 0.70, 0.80, 0.90. Increase in atmospheric pollutants in Mexico City have promoted a gradual decrease in frequency and cover of epiphytic mosses even though some ecological factors may show the oposite effect.
Scanning electron microscopy and light microscopy were used to elucidate the morphology of Metzgeria conjutata Lindb. and confirm the presence of 2 rows of epidermal cells on the dorsal surface, (21-3) rows on the ventral surface, midrib with cells in (3-51-6) tiers; hirsute, short hairs, straight on the thallus-margin and on the ventral surface of midrib; marginal hairs paired, single or in groups of three; male branches globose or subglobose; female involucres obovate and hirsute at the margin, calyptra fleshy, pyriform to club-shaped, hirsute on the outer surface, hairs long and straight.
The vascular flora of Chiapas, Mexico, has been the subject of a long term study by Dennis Breedlove of the California Academy of Sciences. This has stimulated a related project dealing with the bryophyte flora of the region. A collecting expedition in 1988 generated 1420 collections of bryophytes. Specialists from 13 institutions assisted with identifications. Approximately 70% of the collections have been determined. Checklists of species of bryophytes of Chiapas are presented. These lists are based on collections at CAS and literature citations. A total of 364 species of mosses and 310 species of hepatics and hornworts are reported from Chiapas.