The purpose of this study was to identify significant species relationships and underlying ecological gradients characteristic of the Huntingdon Marsh, Quebec. In 1970, one hundred and seven 1-m2 samples of plant biomass were obtained from the marsh in conjunction with environmental measurements. These data were later analyzed using principal-components analysis.The marsh complex divided unambiguously into emergent aquatic and sedge meadow communities on the basis of distinct environmental and compositional differences. Equisetum fluviatile, Scirpus fluviatilis, Eleocharis palustris, and Scirpus validus were major species in the emergent aquatic community. Respectively, these species dominated 29, 25, 16, and 14% of 51 quadrats on a dry weight basis. Water depth accounted for almost one-third of the species variation in this community. Interaction between submerged and floating forms and competitive exclusion between dominant species explained much of the remaining species variance.On a dry weight basis, Carex aquatilis, C. lacustris, Calamagrostis canadensis, and Typha angustifolia dominated 36, 16, 16, and 11% of the 56 quadrats on the sedge meadow. As a group, Carex spp. dominated 63% of the quadrats. Disturbance related to chance perturbations, water depth, and the incidence of fire accounted for much of the variation in this community.The organization of emergent and sedge meadow communities was discussed in relation to continuum and community concepts with particular reference to relative changes in discontinuity of species relationships across the environmental gradient.
MEIOSIS AND POLLEN MITOSIS IN X-RAYED AND UNTREATED SPIKELETS OF ELEOCHARIS PALUSTRIS
