Isoetes ×pseudotruncata, a new triploid hybrid from western Canada and Alaska

A new interspecific Isoetes hybrid, I. echinospora Dur. ×I. maritima Underw., is described from Vancouver Island, British Columbia and southern Alaska by means of cytology and the scanning electron microscopy of spores. Isoetes ×pseudotruncata D.M. Britton and D.F. Brunton, hyb.nov. is the name proposed for this taxon. It is triploid and produces only aborted, sterile spores and has spore ornamentation features intermediate between those of its putative parents. Several concentrations of hybrids have been identified, each growing with both parents in shallow, freshwater habitat along the Pacific Coast of northwestern North America. Keywords: Isoetes echinospora, Isoetes maritima, hybrid, British Columbia.