In young forests of humid south-central British Columbia, Lobaria pulmonaria and other epiphytic “cyanolichens” attain optimum development over the lower branches of conifers growing within the dripzone of Populus. To account for this, we propose the existence of a “dripzone effect”, in which nutrient-rich leachates from the upper branches of Populus enhance the pH of nearby conifers to the benefit of cyanolichen colonization. The dripzone effect is presumably most pronounced in stands located over nutrient-rich soils, in which Populus plays a pivotal role in the early establishment of nitrogen-fixing epiphytic cyanolichens. This phenomenon is assumed to be widespread, but it apparently leads to colonization of conifers by cyanolichens only in humid regions not subject to acid rain. Though the presence of cyanolichens on trees belonging to the Pinaceae is probably indicative of allochthonous nutrient enrichment wherever it occurs, we stress that the dripzone effect is only one of many mechanisms promoting the enrichment of conifer bark.

Usnea pacificana P. Halonen, sp. nov., is reported from the Pacific coast of Canada and the United States. Usnea wasmuthii Räsänen is documented from the states of Washington and Oregon as new to North America. A key to the Usnea species that are similar or related to U. pacificana is provided.

Tortula ruralis is a desiccation-tolerant bryophyte with a novel post-transcriptional gene response to drying and rehydration. To better understand the molecular basis of mRNA stability and selective mRNA translation upon rehydration, 149 T. ruralis cDNAs were selected and analyzed by sequence comparison for the presence of cis-acting elements associated with the formation of mRNA 3′-ends. The cDNAs analyzed were 140 expressed sequence tags (ESTs) isolated from desiccated gametophytes (AI304967–AI305106), a calmodulin-like domain protein kinase (U82087), the rehydrins Tr155 (U40818) and Tr288 (U21679), and six previously unreported ESTs isolated from desiccated gametophytes (AI665854–AI665859). The majority of cDNAs contained within the 3′ untranslated region a consensus AAUAAA poly (A) signal and a highly conserved far-upstream element (FUE) that was similar to the plant consensus GU-rich sequence. The T. ruralis FUE consensus sequence is WUUUUGUUK (where W = A U and K = G U) which we have designated as the UUG-core motif. We have characterized five classes of cDNA's based upon the modular architecture of the poly (A) signal motif. Each cDNA class, with the exception of class V, contained the UUG-core motif. Class I (18% of the total) contained the conserved poly (A) signal sequence 0–30 nucleotides from the poly (A) site. Class II (28% of the total) contained a consensus hexanucleotide 0–30 nucleotides from the poly (A) site. Class III (2% of the total) contained an exact copy of a related poly (A) signal (AAUGAA) more than 30 nucleotides from the poly (A) site. Class IV (20% of the total) contained a consensus hexanucleotide more than 30 nucleotides from the poly (A) site. Class V (32% of the total) contained no known poly (A) signal. Analysis of the relative frequency of sequences between 1 and 60 nucleotides upstream from the poly (A) tail was determined for each cDNA sequence. Overall, the 60 nucleotide sequence was found to be U-rich and C/G poor with an A-rich region between nucleotides 10 and 30. Putative poly (A) signals are arrayed within the 3′ untranslated region of T. ruralis cDNAs as predicted from the angiosperm model systems, including the absence of a conserved unifying cis-acting motif. To our knowledge, this is the first description of the molecular architecture of poly (A) signals within moss cDNAs.

Symphyodon Mont., a genus of pleurocarpous mosses, is comprised of 15 species. Species of Symphyodon, all dioicous, are primarily epiphytic and characterized by having echinate capsules, distally roughened or papillose setae, and prorate leaf cells. The genus is chiefly distributed in the tropical and the subtropical regions of the world with the majority of the taxa centered in southern and southeastern Asia. A detailed study of the peristome structure supports recognition of Symphyodon in its own family, Symphyodontaceae. The family is retained in the Leucodontales, suborder Neckerineae. All species are illustrated. Keys, descriptions, and distribution maps are provided.

The West Indian moss flora, with about 714 species and varieties, is widely represented in North America (Mexico), Central and South America. There are northward and southward trends in the distribution of taxa that suggest, along with the overall similarity of the moss flora of each area, that mosses dispersed to Cuba, Jamaica, Hispaniola, and the Lesser Antilles in Pliocene and Pleistocene times. A vicariant event is not favored as the explanation for most patterns of distribution, because much of the islands' surface was underwater when rafting was completed. A dendrogram resulting from an UPGMA cluster analysis of the similarity matrix shows that Haiti, Dominican Republic, and Jamaica exhibit floristic differences among them and with their neighbors that seem to be consistent with the a non-vicariant origin of the moss floras.

Cololejeunea pocsii Tixier, known only from Vietnam, is proposed as a synonym of Cololejeunea filicis (Herzog) Piippo. Detailed description, illustration, and a distribution map of C. filicis are provided.

Based on morphology, Sphagnum cuspidatum and S. viride have been recognized as two different species. Morphs corresponding to the two taxa were investigated in nine populations situated in Norway, Denmark, Canada, and U.S.A. Eleven putative isozyme loci were used to map genetic variation and to assess the taxonomic relationships. Cluster analysis of allele frequency data did not produce groups corresponding either to the two species or to geographic regions. Low evolutionary rates because of low mutation rates and large effective population sizes may account for the lack of divergence between populations, even across continents. A test of population differentiation showed significant divergence between the two morphs in one population indicating that they might be reproductively isolated. However, in five other populations containing both morphs no such patterns were found suggesting that the speciation process is incomplete. A species level recognition of these taxa is not supported by isozyme data, rather taxonomic recognition at the subspecific level may be more appropriate. A population of S. trinitense expressed unique allele combinations, supporting the view that it is a distinct species different from S. cuspidatum.

Two sorediate counterparts of Fuscopannaria leucosticta (Tuck.) P. M. Jørg. are described: F. coerulescens from Nepal and New Guinea and F. sorediata from eastern North America and Japan. Pannaria cyanolepra (Tuck.) P. M. Jørg. comb. nov., a sorediate species in the F. praetermissa group restricted to California, is transferred to Fuscopannaria, and a key to all known sorediate species of this genus is given.

Spilonemella Henssen & Tønsberg is described as a new genus and placed in the Coccocarpiaceae. The new taxa, S. americana Henssen & Tønsberg and S. japonica Henssen, are described. The species of Spilonemella have a minutely fruticose thallus on a more or less well-developed blue-green prothallus. The photobionts are scytonemoid. The thallus is composed of ascending to erect branched lobes with opuntioid budding. The buds easily break off and function as diaspores. Lobes develop either from diaspores or by lichenization of filaments of the cyanobionts on the prothallus. In apothecial development and structure, the new genus corresponds to those of the related Spilonema, but differs by the presence of a cupular exciple.

Nephroma occultum Wetm. is a rare, epiphytic lichen associated with old-growth forests of northwestern North America. We describe its distribution, abundance, and habitat within the managed landscape of a southwestern Oregon watershed. Because this species is found mainly in the canopy, we used direct canopy access (tree climbing) in combination with ground (litter) searches for our surveys. We recommend this dual approach when confident determination of presence or absence of a canopy species is needed. Our surveys confirm that N. occultum is a rare old-growth associate within the area of this study, the southernmost extension of its known range. It was both rare across the landscape and uncommon in our primary study site, a 500 yr old stand. It was most often found growing close to the trunk on branches of large Pseudotsuga menziesii, but its distribution was sporadic even within an old-growth stand. The scarcity of very old stands, in combination with the limited ability of this species to disperse within and between stands, has likely contributed to its rarity within the watershed. Management for N. occultum should focus on populations and habitat needs rather than on individuals. Our calculations show that cutting with retention of individual trees surrounded by small buffers could result in the eventual loss of N. occultum from the study area.

Bryophytes have been powerful experimental tools for the elucidation of complex biological processes. Analysis of organisms from these ancient clades is an active and ongoing enterprise that will provide greater insight into the development, physiology, phylogenetics, and stress-induced cellular responses of plants. To maintain their relevance as experimental models, the analysis of mosses must expand to include modern molecular tools such as a knowledge of the genome via large-scale DNA sequencing, the ability to create transgenic individuals via transformation, and the capability to create gene knock-outs by homologous recombination. The availability of these molecular tools is limited when compared to flowering plants. However, in mosses such as Physcomitrella patens, Funaria hygrometrica, Ceratodon purpureus, and Tortula ruralis these tools are rapidly being developed for the study of molecular genetics. Efficient targeted gene disruption (i.e., homologous recombination) is a well-established tool in both yeast and murine cells that until recently was unknown in any plant model system. Recently, Schaefer and Zryd (1997) demonstrated that efficient homologous recombination occurs in P. patens. The ability to perform efficient homologous recombination in P. patens is at present unique amongst all plants and represents an extremely powerful technique for the functional analysis of plant genes.

A new species, Gyalectidium yahriae Buck & Sérus., is described from collections made on twigs in Quercus woods in Florida (U.S.A.) and from decorticated wood in the montane forest zone of Papua New Guinea. Its ascocarps are unknown, but it is easily characterized by hyphophores composed of a circle of triangular lobes and by masses of moniliform hyphae producing long cilia on their outer cells; its generic position in the lichen family Gomphillaceae is uncertain.

The new species L. lichexanthona Guderley, L. notatica Guderley, L. rabdotoides Guderley, and L. xanthoplumosa Guderley are described from tropical South America. All the new species have unusual chemistries. Confluentic, notatic, and subnotatic acids present in L. notatica and norlichexanthone present in L. lichexanthona have not been reported previously for the L. subfusca group.

Calymperes venezuelanum (Mitt.) Pitt. (Musci, Calymperaceae), with a scattered range in central and northern, tropical South America, is reported for the first time from Africa on a single collection from Madagascar. The presence of young and mature sporophytes in the material allows description of the sporophyte, which was previously unknown.

Cleistocarpous mosses, those lacking a differentiated operculum and having the capsule dehisce irregularly, are generally thought to have evolved via reduction from stegocarpous ancestors. Bruchia (Bruchiaceae), a cleistocarpous genus of approximately 15 species, shares gametophytic similarities with the genus Trematodon, which has a functional annulus and dehiscent capsule. The sequence of cell divisions characterizing the sporophyte of Bruchia flexuosa shows that development is typically haplolepideous up to the stage in which the peristomial formula is 4:2:2. Whereas other haplolepideous species, including Trematodon longicollis, complete development with a 4:2:3 peristomial formula, the last set of anticlinal divisions in the Inner Peristomial Layer do not occur in B. flexuosa, which therefore appears to mature at what is an immature stage in related stegocarpous taxa. This pattern of development is consistent with an origin of the cleistocarpous capsules of Bruchia through paedomorphosis from a Trematodon-like (haplopideous) ancestor.