Fruits of Vallisneria americana were collected in late September from four sites along the Huron-Erie Corridor, on the Canadian side of this connecting channel between Michigan and Ontario. Some fruits were stored (moist) at 4˚C, and others at 20˚C for 75 days, after which seeds (brown-and white-coloured) were placed in petri plates to germinate. Vallisneria does not have a cold stratification (chilling) requirement for germination, although chilling enhanced percent germination. Testa colour and structure were correlated with seed maturity and germinability: only 30% of the immature white seeds germinated compared with 57% of the larger (mature) brown seeds. Scarification significantly enhanced germination; for example, scarified seeds from Rondeau Bay germinated up to 90% after 60 days, whereas fewer than 30% of non-scarified seeds from that site germinated. Scarified, mature seeds collected from different sites were exposed to various concentrations of the polychlorinated biphenyl (PCB) mixture Aroclor 1260. Overall, in the repeated measures analysis, there were significant effects of treatment, site and time; the high PCB treatment, and the control treatment promoted significantly higher percent germination than the medium and low PCB treatments. Significantly lower % germination was noted for seeds from Mitchell's Bay, overall. Germination of seeds collected from the two more PCB-contaminated sites (Fighting Island and Mitchell's Bay) was not impaired by high levels of PCB (24 µg/L); indeed, for seeds from these sites, the high PCB treatment ranked first in terms of % germination at the end of the study (this difference was statistically significant for Mitchell's Bay). For seeds from the "cleaner" sites (Rondeau Bay and Kettle Point), the highest PCB treatment did not rank first for % germination. This suggests there may be some localized evolution of contaminant tolerance, at least at the stage of germination, or that the biochemical effect of PCBs may be to enhance the process of imbibition, perhaps by increasing membrane permeability.Résumé: Des fruits de Vallisneria americana ont été récoltés, tard en septembre, dans quatre sites échelonnés le long du couloir formé par le lac Huron et le lac Érié, sur le côté canadien de cette voie reliant le Michigan et l'Ontario. Certains fruits ont été conservés (à l'état humide) à une température de 4 °C et d'autres l'ont été à 20 °C pendant 75 jours, après quoi les graines (de couleur brune ou blanche) ont été mises dans des plats de pétri en vue de leur germination. Vallisneria n'est pas une espèce exigeant une période de stratification au froid pour la germination, même si le refroidissement contribue à accroître le pourcentage de germination. La couleur et la structure du péricarpe ont été corrélées avec la maturité des graines et leur pouvoir de germination, seulement 30 % des graines blanches immatures ayant germé par comparaison à 57 % chez les graines brunes matures. La scarification améliore la germination de manière significative; par exemple, les graines ...