The lichen family Cladiaceae is described as new and the genus Cladia comprising seven species is revised.

  A key to the species and a full description of each is provided together with discussions on affinities and chemical constituents. The distribution of each species is discussed and illustrated with maps.

  A complete bibliography to the genus is provided with a bibliographic index.

  The species concept of Pohlia columbica (Kindb. ex Mac. & Kindb.) Andrews is clarified and lectotypified by a Macoun collection from British Columbia dated April 6, 1889 at the Kindberg Herbarium (s). In addition, Pohlia lescuriana (Sull.) Grout is reported here for the first time from western North America.

  Of the nine species names that have been placed in the genus Leiomitrium Mitt. (= Coleochaetium (Besch.) Ren. & Card.) only L. plicatum (P.-Beauv.) Mitt. can taxonomically be retained in the genus. The remaining eight species are more correctly considered either as synonyms of other names in Macrocoma, or in the genus Cardotiella Vitt gen. nova. Leiomitrium is a taxon closely related to Macrocoma with its one species restricted in distribution to the Mascarene Islands. This monotypic genus is best distinguished by creeping stems; a tendency to have imbricate, rounded-obtuse branch leaves; very long ocrea; cylindric, exserted, deeply ribbed capsules; a peristome of 8, reflexed exostome teeth, and 8 (or 16) endostome segments; and plicate, hairy, campanulate calyptrae. Historically, the characters which distinguish this genus have not been interpreted entirely correctly and a discussion of these is given, along with typification of the names that have been placed in the genus. Five of these species form a natural assemblage and deserve to be recognized in a separate genus - Cardotiella - distinguished by creeping stems, uniformly-rounded-quadrate leaf cells with the tendency to be strongly unipapillose; long decurrencies of inflated, tuberculate, hyaline cells; peristome of unfused parts; and non-plicate, basally lobed calyptrae. These features ally this genus to Schlotheimia.

  Four genera, Cryphaea (6 species), Dendropogonella (1 species), Schoenobryum (2 species) and Sphaerotheciella (2 species) are recognized for the area. Two new combinations, Sphaerotheciella pachycarpa (Schimp. ex Besch.) Manuel and Schoenobryum mittenii (Jaeg.) Manuel are made. Descriptions, illustrations, keys and distribution maps, remarks on byrogeography, morphology, nomenclature, and taxonomy are provided.

  Taxonomic problems concerning poorly known and variable taxa of Sphagnum from the Atlantic Coastal Plain were investigated using methods drawn from biometry, experimental taxonomy, and genecology. The methods used in the study of character variation included intensive sampling within individual plants, measurement of microscopic characters, and plotting of histograms and scatter diagrams. Follow-up studies, tailored to the variation observed in each pair of taxa studied, included reciprocal transplants, analysis of herbarium specimens using an adaptation of the hybrid index and an index of dispersion, collections along a local environmental gradient and culture under uniform conditions.

  It was not the intent of this study to carry out systematic revisions of the selected taxa. However, certain specific implications for the taxonomy of the taxa studied were revealed. Variants of S. lescurii Sull. that resemble S. cyclophyllum Sull. & Lesq. could be separated from the latter. Sphagnum fitzgeraldii Ren. & Card. and S. torreyanum Sull. were found to be separated from S. cuspidatum Hoffm. No evidence, however, could be found to support the continued recognition of S. trinitense C. Müll. and S. cuspidatum as separate species. Based on evidence of overlapping characters within plants, erratic variation, and discordant variation in herbarium specimens, the two taxa should be synonymized. The two varieties of S. macrophyllum Brid., var macrophyllum and var. floridanum Aust. should be retained. Habitat forms of S. perichaetiale Hampe and the two varieties of S. imbricatum Russ. should not be recognized.

  An analysis of variance showed that in three taxa variation among individual branch leaves contributed significantly more to the overall variation observed in a clump than did variation among branches or among plants. The evidence needed to support different infraspecific categories in Sphagnum is discussed, and the potential for misuse of mixed collections as evidence in this regard is emphasized.

  Two new species of Notoscyphus Mitt. have been described from eastern Himalayas: N. darjeelingensis sp. nov. from Darjeeling and N. pandei sp. nov. from Gangtok, Kurseong and Shillong. Both these are also represented in south India in Nilgiri Hills. The genus has four species in India including N. lutescens (Lehm.) Mitt. from Darjeeling, Kudremukh and Palni Hills (south India) and N. paroicus Schiffn. from Kudremukh, and Nilgiri Hills. All the four species show differentiating features in sexuality, stem anatomy, nature of leaf cell walls, underleaves, male bracts, female bracts and pseudoperianth.

  The lichen metabolite roccellic acid, as sodium salt, proved to produce a stimulating action in the formation of adventitious roots in cuttings of Tradescantia virginianaL. f. albiflora B. The cuttings were culturated in a nutrient solution with different concentrations of roccellic salt over a period of 16 days. The most stimulatory effect was obtained with the 10^-7 M concentration overcoming those of AIA and kinetin.