The demography, morphology and anatomy of the needle palm Rhapidophyllum hystrix

Rhapidophyllum hystrix is an extremely uncommon palm. This usually acaulescent species inhabits moist sites along floodplains, swamp forests, and ravine systems of the southeastern United States. It has a scattered distribution from central Florida north to Georgia and west to Mississippi. Six new county records were established. Populations of the needle palm ranged from one individual to over 1000.;Two study sites were established to collect data on the demography of Rhapidophyllum. Adults (males and females) were evenly distributed at the primary site but the male to female ratio was 3.4 at the secondary site. In addition, the male to female inflorescence ratio at both study sites was 1.5 and 4.0, respectively. Juveniles were a major component at both sites (45% and 58% respectively), while the seedling population was negligible and does not contribute significantly to the overall population. Attempts to age mature plants proved unsuccessful.;Soil analyses were conducted at four study sites, three of which supported Rhapidophyllum plants. Percent organic matter and nitrogen and soil texture emerged as potentially important factors limiting the distribution of Rhapidophyllum.;A morphological feature which appears to contribute to the poor competitiveness of Rhapidophyllum is its extremely reduced axillary pistillate inflorescence surrounded by spines and leaf bases. Due to this morphology, mature fruits are not dispersed effectively. The fruits often rot while still within the plant crown. Many seeds germinate while still on the plant; these seedlings eventually die after exhausting their food reserves. There does not appear to be an effective seed dispersal agent for the needle palm. The primary mechanism for reproduction in Rhapidophyllum is clonal through the production of ramets.;An extensive study of the morphology and anatomy of the needle palm was made and previously unknown characteristics were discovered for leaf anatomy and reproduction. Polyembryony and apogeotropic roots are reported here for the first time.;The putatively closest relatives of Rhapidophyllum are Trachycarpus and Chamaerops. Although the overall morphology of Rhapidophyllum is quite similar to both Trachycarpus and Chamaerops, the detailed anatomical observations reported here support the separation of Rhapidophyllum from these two genera.