Terrestrial Ferns Research Articles

Microhabitat of small mammals at ground and understorey levels in a deciduous, southern Atlantic Forest

Each animal species selects specific microhabitats for protection, foraging, or micro-climate. To understand the distribution patterns of small mammals on the ground and in the understorey, we investigated the use of microhabitats by small mammals in a deciduous forest of southern Brazil. Ten trap stations with seven capture points were used to sample the following microhabitats: liana, fallen log, ground litter, terrestrial ferns, simple-trunk tree, forked tree, and Piper sp. shrubs. Seven field phases were conducted, each for eight consecutive days, from September 2006 through January 2008. Four species of rodents (Akodon montensis, Sooretamys angouya, Oligoryzomys nigripes and Mus musculus) and two species of marsupials (Didelphis albiventris and Gracilinanus microtarsus) were captured. Captured species presented significant differences on their microhabitat use (ANOVA, p = 0.003), particularly between ground and understorey sites. Akodon montensis selected positively terrestrial ferns and trunks, S. angouya selected lianas, D. albiventris selected fallen trunks and Piper sp., and G. microtarsus choose tree trunks and lianas. We demonstrated that the local small-mammal assemblage does select microhabitats, with different types of associations between species and habitats. Besides, there is a strong evidence of habitat selection in order to diminish predation.

Antibacterial activity of the terrestrial fern Lygodium flexuosum (L.) Sw. against multidrug resistant enteric- and uro-pathogenic bacteria

ObjectiveTo investigate antibacterial properties of the terrestrial fern Lygodium flexuosum (L. flexuosum) obtained from Kalahandi district, Odisha against enteric- and uro-pathogenic bacteria isolated from clinical samples. MethodsFrond-extracts of L. flexuosum were obtained by the cold percolation method using four solvents, petroleum ether, chloroform, methanol and water. Antibacterial potencies of concentrated cold frond-extracts were tested by the agar-well diffusion method against 7 multidrug resistant (MDR) bacteria of which, 2 were Gram-positives, methicillin resistant Staphylococcus aureus (MRSA) and vancomycin resistant Enterococcus faecalis (VRE), and 5 Gram-negatives, Enterobacter aerogenes, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Proteus mirabilis. ResultsThe cold-water frond-extract had the best antimicrobial activity against 7 MDR bacterial isolates, compared to extracts with other solvents. Values of zones of inhibition against MRSA and P. mirabilis were the highest, 29 mm. Zones of inhibition against VRE and P. aeruginosa were 25 mm, while those were 23 mm against E. aerogenes and E. coli. The least size of zone of inhibition 19 mm was recorded against K. pneumoniae. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of active frond-extracts with water, chloroform, methanol, and petroleum ether were recorded. For the water extract, the MIC value 1.562 mg/mL against MRSA and P. mirabilis, but the value 3.25 mg/mL against VRE, E. aerogenes and P. aeruginosa, while the value of 12.5 mg/mL against K. pneumoniae were recorded. MBC values were the least with chloroform-extracts, with the range 12.5 for 6 bacteria, excluding P. aeruginosa for which, the value 25 mg/mL was recorded as MBC. ConclusionsPhytochemical analysis of the water-extract of L. flexuosum confirmed the presence of glycosides and carbohydrates, but alkaloids, terpenoids, steroids, saponins, tannins, and flavonoids were absent. L. flexuosum, being a fern, is a suitable non-microbial source of antimicrobial for MDR strains of major enteric and uro-pathogens.

Ferns in an Angiosperm World: Cretaceous Radiation into the Epiphytic Niche and Diversification on the Forest Floor

The Cretaceous period saw dramatic shifts in the functional plant biology of the Earth’s flora. This was an episode of explosive plant radiations that produced our modern angiosperm-dominated world. This period was also a time of great Pteridophytic diversification and experimentation and saw the rise of most extant fern lineages. Prominent among these was the widespread appearance of epiphytic species. In modern tropical forest canopies, epiphytic ferns often represent some of the most abundant taxa and can dominate epiphyte biomass. Yet from most perspectives, the epiphytic habitat is vastly different from the forest floor. What happened during the Cretaceous that led to such widespread epiphyte fern diversification? What are the traits that allow extant ferns to flourish in this dry, nutrient-poor, bright habitat? How did terrestrial ferns cope with this new habitat? We review a number of functional aspects of fern biology to include both gametophytic and sporophytic physiology. It is possible that angiosperms engineered conditions that lead to aseasonal tropical forests. Data suggest that ferns may have reduced water use efficiency. If so, then wetter forests may have facilitated fern diversification. Successful epiphytic species would have required major modification in the gametophyte generation to include indeterminate growth, extreme stress tolerance, and an outcrossing breeding system. Terrestrial species also radiated at this time and may have relied on unique aspects of photobiology to take advantage of low-light terrestrial habitats. The study of fern ecology has reached a fevered pitch. Continued investigation will no doubt reveal some of the most exciting changes in our understanding of this remarkable lineage.

Drivers of morphological diversity and distribution in the Hawaiian fern flora: Trait associations with size, growth form, and environment

Hawaii is home to 238 native and 35 alien fern and lycophyte taxa distributed across steep gradients in elevation and resource availability. The fern flora spans a wide range of growth forms, with extraordinary diversity in morphology and plant size. Yet the potential factors underlying this diversity have remained enigmatic. We used a trait database generated from the most recent and comprehensive survey of Hawaiian ferns and lycophytes to test hypotheses of size-scaling and trait associations with environment and growth form as factors underlying this diversity. We also tested relationships among morphology, taxon abundance and distribution and identified key differences between native and alien taxa. Strong trait-trait relationships included geometric scaling of plant dimensions with a tendency for more divided fronds in larger ferns. Trait-environment relationships independent of size included more divided fronds at higher elevation, longer blades in shaded habitats, and fronds with shorter stipes and fewer pinnae in drier habitats. Growth forms differed in mean size with epiphytic and epipetric taxa smaller than terrestrial ferns. Plant size was independent of taxon abundance and distribution across islands, and native and alien ferns did not differ in mean size. Alien taxa were more abundant, especially at lower elevations, apparently due to human land use. These relationships point to linkages of fern form and demography with biogeography and highlight potential flora-scale physiological and morphological adaptations in ferns across contrasting environments.

The impact of sterile populations on the perception of elevational richness patterns in ferns

Dispersal may influence the spatial distribution of species richness through mass or source-sink effects, but the extent of sink populations at the community level remains largely unknown due to difficulties of identifying such populations. We compared the richness patterns of ferns in 333 plots along six tropical elevational gradients in America, the Mascarenes, and southeast Asia, using sterile populations as an indication of sink populations. First, we tested whether sterile fern records were more common towards the elevational range limits of the individual species, but found this pattern in only one out of ten cases. It is therefore uncertain if sterile records correspond to marginal sink populations. Second, we compared the elevational richness patterns of sterile and fertile species. In several cases, elevational trends for sterile and fertile records were quite similar, but in others they differed distinctly. The percentage of sterile records per plot decreased with elevation among epiphytic ferns along all six transects, whereas terrestrials showed mixed results (decrease, increase, and U-shaped patterns). The percentage of sterile species records per plot relative to the number of species per plot recovered four significant patterns among the twelve cases analysed: higher percentages at higher species numbers among terrestrial ferns on two transects and lower percentages among epiphytes on two others. Despite the problems with equating sterile records to sink populations, we thus found distinct elevational patterns of sterile records that clearly affected our perception of the overall richness patterns. Ignoring the impact of population dynamics on diversity patterns is thus liable to result in misinterpretations of the diversity patterns.

Hydraulic properties of fern sporophytes: Consequences for ecological and evolutionary diversification

Ferns are an important component of both tropical and temperate forests; yet, our understanding of the water relations of their sporophyte generation is limited. Indeed, to date there has been no large scale survey that attempts to clarify how ferns fit into current ideas of plant water relations. This study examines several tropical ferns with the goal of understanding how these characters vary between species from various habitats and across life forms • We measured stipe hydraulic conductivity, water potential, and vulnerability to cavitation along with photosynthetic variables and leaf allometry of 21 species from 14 genera to identify physiological trait assemblages across taxa. • Epiphytic ferns have significantly lower hydraulic conductivity and a vascular system more resistant to cavitation (i.e., higher P(50) values). They reached lower mid-day water potentials and produced leaves with reduced stipe lengths and reduced laminar area relative to terrestrial species. Xylem specific hydraulic conductivity (K(S)) was correlated with the mean hydraulic diameter of tracheids in terrestrial species, but not in epiphytes. There was no evidence of safety-efficiency trade-offs in any group. • When compared across life forms, our data shed light on physiological mechanisms that may have allowed for terrestrial ferns to move into the epiphytic habit. When compared across a diverse assemblage of terrestrial plants, we find that resistance to water flow in fern stipes is significantly higher than that recorded from the stems of seed plants.

Epiphytes and hemiepiphytes have slower photosynthetic response to lightflecks than terrestrial plants: evidence from ferns and figs

Abstract:Photosynthetic responses of 12 species including six fern species (Neottopteris nidus, Microsorum punctatum, Pseudodrynaria coronans, Asplenium finlaysonianum, Paraleptochilus decurrens and Tectaria fauriei) and seedlings of six fig species (Ficus curtipes, F. gibbosa, F. altissima, F. auriculata, F. oligodon and F. hookeriana) in different life forms to lightfleck were investigated, to test whether epiphytes and hemiepiphytes display a slower response to lightfleck and fast induction loss after a lightfleck compared with their terrestrial counterparts, and whether ferns display a slower response to lightfleck and slower induction loss compared to figs. The measurements of functional traits and physiological parameters were determined in a screenhouse of 4% full sunlight. Epiphytic ferns and hemiepiphytic figs had thicker leaves compared with their terrestrial counterparts. Compared with figs, ferns had thicker fronds, larger stomata with a low density, and lower stomatal conductance and photosynthetic capacity; ferns had lower light compensation point and dark respiration rate, conferring a positive carbon gain under low diffuse light beneath the canopy. The induction time to reach 90% maximum net photosynthetic rate (T90) upon the exposure to a saturated light varied strongly among life forms. Epiphytic ferns had slower T90 than terrestrial ferns (19.9–26.3 vs 5.9–16.3 min, respectively), and hemiepiphytic figs had slower T90 than terrestrial figs (13.1–20.4 vs 5.2–7.8 min, respectively). Compared with figs, ferns showed a slower response to lightfleck. Across ferns and figs, the induction time was negatively correlated with initial stomatal conductance. No significant difference in induction loss was found between two life forms within ferns or figs, whereas ferns had a significantly slower induction loss compared with figs. These results showed that the inherent conservative water use strategy of the epiphytes and hemiepiphytes constrain their lightfleck utilization.

Habitat Differentiation of Ferns in a Lowland Tropical Rain Forest

Fern species and growth form diversity peak in tropical rainforests. In such forests, ferns often play important ecological roles. However the distribution and diversity patterns of different growth forms (i.e., epiphytic vs. terrestrial ferns) have not been broadly quantified. We compared the distribution and diversity patterns of epiphytic pteridophytes on the trunks of six individuals of the emergent canopy tree species Hyeronima alchorneoides (Euphorbiaceae) to those of terrestrial species at La Selva Biological Station in Heredia province, Costa Rica. A total of 21 species of epiphytic and 20 terrestrial ferns was recorded, with only one species found as an epiphyte and as a terrestrial species. Epiphytic species also exhibited increasing species diversity with increasing trunk height. Epiphytic species exhibited predictable patterns of distribution along the trunk and were easily grouped into high-trunk, low trunk, or bimodal categories. In terms of percent cover and number of species, simple-leaved ferns dominated the epiphytic growth form, 13 of 21 species, whereas ferns with compound or dissected leaves dominated the hemi-epiphytic and terrestrial floras with 20 of 20 species. These results indicate that there are significant functional differences in the ecology of epiphytic and terrestrial ferns and that reciprocal establishment is difficult and extremely rare.

Antiinflammatory and antinociceptive activities of Blechnum occidentale L. extract

Aim of study Blechnum occidentale L. is a terrestrial fern that ranges from the United States to South America, and is employed in Brazilian folk medicine. In the present study we investigated the antinociceptive and antiinflammatory activities of the methanolic extract of Blechnum occidentale L. (MEB) in animal models of pain and inflammation to support its medicinal use in treatment of inflammatory and pulmonary diseases, urinary infections and liver diseases. Materials and methods The antinociceptive activity of MEB was evaluated using the writhing, formalin, and tail flick tests. The antiinflammatory activity of MEB was evaluated in carrageenan-induced paw oedema and neutrophil migration. In order to discard possible non-specific muscle relaxant or sedative effects of MEB, mice motor performance was evaluated in the rota rod test and its toxicity evaluated over 14 days. Results Intraperitoneal (IP) administration of MEB (0.01–100 mg/kg) produced a dose-related antinociception on acetic acid-induced writhing in mice. Oral administration of MEB, at a different range of doses (100–400 mg/kg), also produced significant antinociceptive effect on the writhing test. Furthermore, treatment with MEB (100 and 200 mg/kg IP) inhibited significantly both the early and late phases of formalin-induced hypernociception in rats. In contrast, treatment with MEB (100 and 200 mg/kg IP) did not prevent the thermal nociception in the tail flick test. The IP administration of MEB (100 and 300 mg/kg) significantly reduced the paw oedema induced by carrageenan. Moreover, systemic treatment with MEB (11–300 mg/kg) reduced the neutrophil migration in the carrageenan-induced migration to the peritoneal cavity. In the rota rod test, MEB-treated mice did not show any significant motor performance alterations with the dose of 300 mg/kg. In addition, over the study duration of 14 days, there were no deaths or toxic signs recorded in the mice given 100 or 1000 mg/kg of MEB. Conclusion The results described here are the first report of pharmacological studies of Blechnum occidentale L. and indicate that this plant has antinociceptive and antiinflammatory activities which support its folk medicine use.

The effect of drought on photosynthesis in two epiphytic and two terrestrial tropical fern species

Water-withholding for 5 to 7 weeks and subsequent re-watering were made on potted plants of two epiphytic (E) and two terrestrial (T) fern species, which were collected from a seasonal tropical rainforest and had been grown in a screenhouse with 5 % irradiance for 4 months. During the water stress, the two E species completely closed stomata when frond relative water content (RWC) reached about 70 % with fairly constant maximum photochemistry efficiency (Fv/Fm), while the two T species kept partial stomata opening until RWC reached 45 % and reduction in Fv/Fm at the late stage. Also, chlorophyll content as indicated by a spectral reflectance index was gradually reduced in three species. Physiological recovery was completed after 3-d re-watering for the E species, which was more rapid than for the T species. The gas exchange measurements and regression analyses indicated higher photosynthetic water use efficiency in the E species than in the T species.

Morphology and evolution of epiphytic Davalliaceae scales

The scales of most members of the Davalliaceae and related epiphytic, secondary-hemiepiphytic, and climbing ferns consist of a stalk and a shield, are dense, and are persistent on the long-creeping rhizomes. They differ from the sessile, mostly deciduous scales of the related terrestrial eupolypod ferns. The stalked scales first developed two-dimensionally and later produced the proximal part of the shield from near the base to comprise a peltate or pseudopeltate shield on a stalk. Anatomical observations showed variations in the cellular and histological features and the degree of stalk insertion into a rhizome concavity. A character-phylogenetic tree of scales suggested an evolutionary linkage between the stalked scale and the epiphytic life form in the lineage leading to Davalliaceae and Polypodiaceae. The elaborated scales of most species of the obligate-epiphytic Davalliaceae were similar to the sunken-stalked, peltate, absorbing, epiphyllous trichomes of some angiosperm epiphytes. These results suggest that the stalked scales may have significant roles such as protection against desiccation, external water storage, and absorption of water and nutrients.

Effects of pH, temperature and light intensity on spore germination and growth analysis of young sporophytes of Polypodium lepidopteris (Pteridophyta, Polypodiaceae)

ABSTRACT Polypodium lepidopteris is a terrestrial fern from coastal vegetation, and is used as medicinal. This work analyzed the effects of pH, temperature and light levels on the spore germination and the relative growth rate (RGR) of young sporophytes. Fertile fronds were collected in Florianópolis, SC, Brazil. The effect of pH (4.0 to 6.7) on spore germinability was observed in a growing room at 25 ± 2ºC (22 mmol m-2s-1) under a 16h photoperiod. No statistical differences between treatments were found. The effect of different temperatures on the germinability was analyzed (20, 25 and 30ºC). The test was carried out in a germination chamber (17 mmol m-2s-1) under a 16h photoperiod. The germination was inhibited at 30ºC. The effect of natural light levels (54, 38, 22 and 8%) was analyzed. The highest germination percentages were verified at 22 and 8% of natural light. The growth analyses show statistical differences in the number of fronds and height of the longest frond between time 1 (283 days of spore inoculation) and time 2 (343 days of spore inoculation). Sporophytes of P. lepidopteris produced 1.33 ± 0.09 fronds per month. The RGR (relative growth rate) was 0.15 ± 0,009 cm cm-1month-1.

Level of trace elements in Pteridophytes growing on serpentine and metalliferous soils

AbstractA screening of Pteridophytes growing on serpentine and metalliferous soils in Northern Italy was carried out to assess the ability of these plants to tolerate or accumulate trace elements of toxicological interest. Few data are available on metal tolerance/accumulation of terrestrial ferns growing in the Mediterranean region, and several species presented here have never been investigated for this purpose. The trace‐element composition (As, Cd, Cr, Cu, Fe, Ni, Pb, Zn) and P content of aerial parts of plants (12 fern and 2 horsetail species) and of their associated soils were measured. An analysis of the relationship between element concentrations in soil and in shoot revealed a significant correlation only for Zn (p < 0.05). Hierarchical cluster analysis based on element concentrations in plant aerial parts showed two outliers, viz. Equisetum ramosissimum Desf., showing the highest levels of Cr, Fe, Cu, Ni, and As, and Nephrolepis cordifolia C. Presl., showing the highest Pb value. The bioaccumulation factor exceeded 1 only for Cd in two species, Athyrium filix‐femina and Dryopteris filix‐mas. However, also in these cases the corresponding values of the metal in the shoots were below the thresholds for hyperaccumulators. The examined Pteridophytes seem to have developed their adaptation prevalently through mechanisms of tolerance based on metal exclusion. None of these plant species seem suitable for phytoextraction, but N. cordifolia, Pteridium aquilinum ssp. aquilinum, and E. ramosissimum have potential to be used for stabilization and restoration of soils rich in heavy metals.

The influence of life form on carbon and nitrogen relationships in tropical rainforest ferns

Tropical ferns are characterized by a high diversity of plant life forms, yet there have been few large-scale studies on the functional ecology of these different forms. We examined epiphytic, hemiepiphytic, and terrestrial ferns, and asked whether there are differences in the mineral nutrition and water relations across different growth forms of a diverse assemblage of species. We measured specific leaf area, leaf nitrogen concentrations, and natural abundance of the stable isotopes delta(15)N and delta(13)C of 48 fern species from 36 genera across a wide range of habitats at La Selva Biological Station in Costa Rica. We found that epiphytes were significantly different in all measured variables from hemiepiphytic and terrestrial species, and that terrestrial and soil-rooted hemiepiphytes were indistinguishable in all variables excluding SLW. A multivariate analysis revealed that aspects of N nutrition were the most reliable at separating epiphytic species from other life forms. Our study demonstrates that the natural abundance of both C and N as well as N relations and leaf morphology are useful when segregating different plant life forms, and that the N cycle of epiphytic and terrestrial habitats function independently from each other.

Gametophyte ecology and demography of epiphytic and terrestrial tropical ferns

Factors that influence the distribution of ferns are poorly understood and likely reflect the ecology of both the sporophyte and the gametophyte generation. Little study has been done on the ecology of the gametophyte generation, especially in regard to tropical species. The goal of this study was to examine demography and the influence of light and disturbance on the distribution of the gametophytes of several tropical epiphytic, hemiepiphytic, and terrestrial fern species. Through a series of observational and experimental studies, we found that increased terrestrial gametophyte density and richness were related to both increased light and disturbance. By contrast, increased light had no influence, and increased disturbance negatively affected epiphytic density. Over a 25-mo demographic study, epiphytic and hemiepiphytic species had significantly greater longevities and lower recruitment rates than terrestrial species. Such unique strategies may have evolved in response to different disturbance regimens between the two habitats. Terrestrial species encounter and are adapted to more frequent disturbance and have invested in rapid gametophyte growth and recruitment. Epiphytic species may be more influenced by bryophyte competition, and in habitats of relatively low disturbance, they have invested in greater size and longevities. In such systems, gametophytes are able to survive for years waiting for favorable recruitment conditions.

Gametophyte Morphology in Three Mexican Species of Bolbitis (Lomariopsidaceae)

The development of gametophytes in Bolbitis bernoullii, B. portoricensis and B. umbrosa (Lomariopsidaceae) is described and compared. Spores are monolete, ellipsoid with prominent winged perispore. Germination is of the Vittaria type and the prothallial development is of the Drynaria type. Collenchyma-like thickenings at the corners of the wing cells were not observed. Adult gametophytes are cordate with scarce marginal hairs near the shallow notch. Gametangia are of the common type found in homosporous leptosporangiate ferns. Bolbitis portoricensis develops the first leaf of the sporophyte after 6 to 8 months, with polocytic stomata. In B. portoricensis, vegetative propagation is present in old thalli 6 to 8 months after cultivation. The genus Bolbitis is a terrestrial or hemiepiphyitic fern, with dimorphic leaves and simple or pinnate blades. Some species have laminar buds, and all have fertile leaves with acrostichoid sori, and reticulate venation with or without included veinlets. Its spores are monolete, non-chlorophyllous, and winged (Mickel and Smith, 2004; Moran, 1995; Tryon and Tryon, 1982; Tryon and Lugardon, 1991). The genus contains about 45 species, a third of which are found in the New World; seven occur in the southeastern part of Mexico. These seven species grow between 0-1300 masl in very wet rainforests. Except for B. portoricensis (Spreng.) Hennipman, all species are uncommon or rare in Mexico. The gametophyte morphologies are known for several Indian species: Bolbitis semicordata (Moore) Ching, B. quoyana (Gaud.) Ching, B. subcrenata (Hook. et Grev.) Ching in C. Chr. (Nayar, 1960; Nayar and Kaur, 1964a, 1964b, 1965a, 1965b, 1965c, 1971); and for Old Word species such as B. angustipinna (Hayata) Ito, B. heteroclita (Presl) Ching and B. repanda (Bl.) Schott (Hennip- man 1970, 1977). In general terms, the mature prothallus of Bolbitis is cordate- thalloid, wider than long, with a dense, 6 to 8-celled thick cushion, and wide flat wings. Collenchyma-like thickenings are present in the corners of wing cells of some Indian species. Gametophytes of Bolbitis can be morphologically different. For instance, the prothallus in B. repanda is cordate, with pluricellular branched hairs and, when old, has a lobed thallus. In B. cladorrhizans (Spreng.) Ching, the gametophyte is glabrous and ribbon-shaped or lobed. Other species such as B. heteroclita have cordiform-spatulate prothalli, with unicellular, secretory and papillate hairs sparsely distributed along the margin of the adult gametophyte. In species such as B. semicordata, B. quoyana and B. subcrenata, the adult cordate thallus is usually branched but may be un-branched and has club-

Terrestrial pteridophytes as indicators of a forest-like environment in rubber production systems in the lowlands of Jambi, Sumatra

Species richness of terrestrial ferns and fern allies (Pteridophyta) may indicate forest habitat quality, as analysed here for a tropical lowland area in Sumatra. A total of 51 standard 0.16 ha plots in primary forest, rubber (Hevea brasiliensis) agroforests and rubber plantations was compared for plot level diversity (average number of species per plot) and landscape level diversity (species–area curves). Average plot level species richness (11 species) was not significantly different amongst the three land use types. However at the landscape level the species–area curve for rubber agroforests (also called jungle rubber) had a significantly higher slope parameter than the curve for rubber plantations, indicating higher beta diversity in jungle rubber as compared to rubber plantations. Plot level species richness is thus not fully indicative of the (relative) richness of a land use type at the landscape scale because scaling relations differ between land use types. Terrestrial fern species can serve as indicators of disturbance or forest quality as many species show clear habitat differentiation with regard to light conditions and/or humidity. To assess forest habitat quality in rubber production systems as compared to primary forest, terrestrial pteridophyte species were grouped according to their ecological requirements into ‘forest species’ and ‘non-forest species’. Species–area curves based on ‘forest species’ alone show that the understorey environment of jungle rubber supports intermediate numbers of ‘forest species’ and is much more forest-like than that of rubber plantations, but less than primary forest. Species richness alone, without a priori ecological knowledge of the species involved, did not provide this information. Jungle rubber systems can play a role in conservation of part of the primary rain forest species, especially in areas where the primary forest has already disappeared. In places where primary forest is gone, jungle rubber can conserve part of the primary forest species, but large areas of jungle rubber are needed. In places where primary forest is still present, priority should be given to conservation of remaining primary forest patches.

A preliminary study on the carcinogenicity of the common fern Onychium contiguum.

Onychium contiguum (Family Cryptogrammaceae) is a common terrestrial fern in the Himalayas and in many other parts of the world. It is also present on the pastures in areas where grazing animals suffer from bovine urinary bladder cancer. This fern is occasionally grazed by animals and in some areas it is present as a contaminant in grasses stored for winter feeding. Certain species of the genus Onychium are used in folk medicine. Long-term exposure of experimental animals to O. contiguum appeared to cause tumours of the ileum. urinary bladder and mammary glands.

Comparative Gametophyte Morphology of Selected Species of the Family Polypodiaceae

Gametophyte morphology and growth habit of seven epiphytic species of six genera in the Polypodiaceae are described. In addition to the Drynaria-type of early development, de- picted previously in most of this family and expressed in all species observed, the Ceratopteris- type, Adiantum-type, and Aspidium-type also occurred in some of the species observed. All spe- cies observed were long-lived, clone-forming, and without gemmae. The long-lived, clone-forming habit increases the space and time occupied by gametophytes, and thus enhances the probability of interaction with other gametophytes and the probability of intergametophytic mating in epi- phytic habitats. Gametophyte morphologies vary greatly beyond the standard heart shapes usually depicted in textbooks (Atkinson and Stokey, 1964; Nayar and Kaur, 1971; Atkinson, 1973). These variations include the ability to grow indeter- minately and to branch, so that perennial gametophyte clones of considerable size may be produced. In some families, gametophytes also have the ability to reproduce themselves vegetatively by dispersable gemmae (Farrar, 1993a, b; Raine, 1994; Dassler, 1995). Gemma production and/or clonal growth have been observed primarily in epiphytic species. Although most of the variation in gametophyte morphology is among epi- phytic species, most of the information known on reproductive biology is from research on terrestrial ferns. Epiphytic ferns exist in an environment very dif- ferent from that of terrestrial species. The gametophytes of tropical epiphytic species are often found within dense bryophyte mats (Dassler, 1995). In such habitats, interaction between gametophytes via chemicals (antheridiogen) and sperm transfer may be significantly hindered relative to gametophytes of ter- restrial ferns on smooth surfaces (Dassler, 1995). Gametophyte persistence and expansion by clone formation may help to overcome these difficulties and promote reproduction in the aerial habitat. In order to assess the significance of morphological diversity to fern reproduction in different habitats, further knowledge of the morphology of gametophytes in epiphytic species is needed. Most species of Polypodiaceae are epiphytic (Lellinger, 1985). We observed the morphology of the gametophytes of seven epiphytic species from this fam- ily. Results are interpreted with respect to modes and mechanisms of the spe- cies' reproductive biology.

Antheridiogen production and response in Polypodiaceae species

Antheridiogen chemicals secreted by living fern gametophytes have been shown to influence production of male gametangia and thus mating systems in a large number of terrestrial fern species. Antheridiogens have not previously been thought to be prevalent in the Polypodiaceae, a large family composed mostly of tropical epiphytes. This study presents bioassay methods more sensitive than previously used to detect antheridiogen and demonstrates that antheridiogens are also operative in the Polypodiaceae and in epiphytic species. Seven species in six genera (Campyloneurum angustifolium, C. phyllitidis, Lepisorus thunbergianus, Microgramma heterophylla, Phlebodium aureum, Phymatosorus scolopendria, and Polypodium pellucidum) were tested for the presence of an antheridiogen system. All species tested except P. aureum were induced to produce antheridia precociously by their own antheridiogen and by that of Pteridium aquilinum (APt). Phlebodium aureum responded to APt and promoted antheridium formation in Onoclea sensibilis but did not respond to its own antheridiogen. Spores of all species except P. aureum were induced to germinate in darkness by antheridiogen of the same species and by APt and to form antheridia in the dark, further enhancing the possibility of intergametophytic mating.