A new Isoetes hybrid (Isoetes echinospora × riparia) for Canada

Abstract

A new interspecific hybrid in Isoetes, Isoetes echinospora Dur. × Isoetes riparia Engelm., is delineated by means of cytology and scanning electron microscopy of spores from the Ottawa–Hull district of Canada. The hybrid should be known as I. × dodgei A. A. Eaton pro sp. This triploid hybrid (2n = 33) exhibits polymorphic megaspores and hybrid vigour. The megaspores of some of the hybrids are extremely spiny, with many fused and irregular spines resulting in convoluted and distorted surfaces. Distribution maps for three species, I. echinospora, I. riparia, and I. macrospora Dur., as well as one hybrid, I. × dodgei, are presented for the Ottawa district.