Alliaria petiolata (garlic mustard), an exotic plant species, has invaded woodlands in several areas in mid‐western and northeastern United States and adjacent Canada, and it is displacing the indigenous under‐story flora. This study was conducted to provide information about the species' biology that might be useful in controlling its spread in native woodlands. The plant is a strict biennial in North America, spending the first year of growth as a basal rosette. This period of relatively slow growth is followed by a period of rapid shoot elongation (1.9 cm/day) during early spring of the second growing season. The plant is capable of cross‐ and self‐pollination, although pollination and stigma receptivity occur before the flower is open, so autogamy is the most likely breeding system. Garlic mustard invests 20.4% of its biomass in reproductive effort, with an annual seed rain of 15,000 seeds/m2. Seed dispersal from fruits begins in early July and continues into October. Most seeds germinate in the spring following the year in which they were produced. Seedling recruitment is high (8.3–18.0 seedlings/cm2), but only about 7.5% of the plants survive to maturity. The success of the plant in invading woodlands appears to be related to (1) its autogamous breeding system that allows a single individual, or a few individuals, to establish populations of genetically similar but interfertile individuals; (2) high seed production, permitting establishment of large numbers of individuals; and (3) rapid growth during the second growing season, which increases its competitive ability. Because of garlic mustard's ability to occupy understory habitats successfully, it may be unrealistic to expect to eliminate the plant from many habitats it has already invaded.

The phonon density of states and adiabatic sound velocities were measured on fcc-stabilized 242Pu0.95Al0.05. The phonon frequencies and sound velocities decrease considerably (soften) with increasing temperature despite negligible thermal expansion. The frequency softening of the transverse branch along the [111] direction is anomalously large ( approximately 30%) and is very sensitive to alloy composition. The large magnitude of the phonon softening is not observed in any other fcc metals and may arise from an unusual temperature dependence of the electronic structure in this narrow 5f-band metal.

We report zero-field inelastic neutron scattering experiments on a deuter-

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Neutron diffuse scattering in the form of rod-like features has been observed in single crystals of the layered CMR material La2−2xSr1+2xMn2O7 (x=0.4,0.36), consistent with the presence of 2D ferromagnetic spin correlations. These diffuse features are observed over a wide temperature region. However, their coherence length does not appear to diverge at TC, although there is evidence of the development of three-dimensional correlations around ferromagnetic reflections of the 3D-ordered magnetic structure close to TC. Quasi-elastic neutron scattering on a ceramic sample of x=0.3 shows that the lifetime of these ferromagnetic correlations increases at T→TC. They exhibit a spin-diffusion constant above TC of ∼5 meV Å2, much lower than that reported for La2/3Ca1/3MnO3. We discuss the relationship of these magnetic correlations to models of the ferromagnetic transition in CMR compounds.

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