ON SOME ABERRATIONS OF EXTANT HORSETAILS (EQUISETUM L.) AND THE ORIGIN OF THE FAMILY EQUISETACEAE

Abstract

Aberrations of the extant species Equisetum hyemale L. are described. In one type of aberrations, the strobili are laterally disposed on short secondary shoots, thus resembling the arrangement of strobili in Mesozoic members of Equisetites and Neocalamites (Equisetaceae). Other types of aberrations in fertile organs of the extant horsetails are also analyzed. These aberrations repeat characters of the Paleozoic (Permian) genera Equisetinostachys, Paracalamitina, and Sendersonia (Tchernoviaceae). Reduction of both vegetative and reproductive organs in members of the Tchernoviaceae leading to the morphological patterns characteristic of the modern horsetails is traced.