HAMMEN, S. C. L. (Department of Botany, University of Rhode Island, Kingston, RI 02881). Density-dependent phenotypic variation in the hay-scented fern, Dennstaedtia punctilobula. Bull. Torrey Bot. Club 120: 392-396. 1993.-Morphological features of the hay-scented fern Dennstaedtia punctilobula. (Michx.) Moore from discrete patches of average area 23.0 ? 8.7 m2 that occurred in a research forest in West Greenwich, Rhode Island were studied to (1) establish typical features of sporophyte morphology, (2) compare the amount of variation between areas of greater and less density within the patches, and (3) to determine which traits were fixed characteristics of this species and which were responsive to environmental stress. Samples were taken over two years. In terms of biomass, fronds made up 46-63% of a sample, rhizomes 34-50%, and roots 2.6-4.5%. The fraction of fronds bearing sori was constant over two years at 76 ? 1%, and the fraction of fronds with epipetiolar buds was constant at 22 ? 1%. The number of sori per pinnule in a sample ranged from 0-23 and was correlated with the length of the frond, which ranged from 36-130 cm. Sporophylls from regions of low density ( 80 fronds/M2). Rhizomes near the center of a patch had fewer nodes, shorter internodes, and larger branching angles than those near the periphery.