Abstract

Hypoglossum imperfectum is described as new to science. It is a minute repent species collected in relatively deep water off the South African south coast, in the Tsitsikamma Coastal National Park. It differs from all other species of the genus by the possession, in fertile blades only, of stunted proximal third-order cell rows, which thus do not reach the thallus margin. This is in violation of the generic definition that proclaims that in Hypoglossum (and the ‘Hypoglossum group’) all third-order cell rows reach the thallus margin.