Notes on the bryophyte communities oe lowland Tropical Rain Forest,with special reference to Moraballi Creek,British Guiana

Discussion and conclusions The four main bryophyte synusiae in the Moraballi Creek rain forest (high epiphytes, shade epiphytes, epiphyllae, synusia on dead wood) are remarkably distinct both in structure and floristic composition, though there are a few very frequent species, e.g. Calymperes lonchophyllum, Octoblepharum albidum, which occur in all the synusiae except the epiphyllous, which consists almost entirely of highly specialised species exclusive to itself. The differences in the structure of the synusiae depend on the different growth forms of the more abundant species. Data are not available for a satisfactory analysis of these growth forms (like that, for instance of Gimingham & Robertson, 1950, for some British bryophyte communities), but from the general observations given above it is obvious, for instance, that there are wide differences between the growth forms of the strongly xeromorphic high epiphyte synusia and those of the shade epiphyte synusia, characterised by markedly hygromorphic features such as freely projecting or dangling shoots and large thin-walled cells. Again, there are conspicuous differences between the growth forms prevailing in the shade epiphyte and dead wood communities. The differences in floristic composition and structure between the various bryophyte synusiae reflect the marked differences in microclimatic and other ecological factors existing between the various microhabitats available for bryophytes within the rain forest community.When the bryophyte synusiae of the Moraballi Creek rain forest are compared with those of temperate deciduous or coniferous forests the most striking differences seen are the absence in the former of any bryophyte synusia on the ground, the presence of an epiphyllous community and the pronounced dominance of hepaticae, especially of the family Lejeuneaceae, in all microhabitats except the dead trunks and stumps. In conclusion it may be noted that the bryophyte flora of the lowland rain forest is not excessively rich in species, indeed area for area it is probably poorer than many temperate forests. The comparatively restricted bryophyte flora, compared with the overwhelmingly rich angiosperm flora is a surprising fact. These comparisons, though based in the first place on the Moraballi Creek forest alone, would apply to lowland rain forests in Africa or the Indo-Malayan region. In montane forests conditions differ greatly from those in the lowlands and some of the above conclusions no longer apply.Received for publication 11.XI.1953.