Primary Basic Chromosome Numbers in Ferns: Facts or Fantasies?

Abstract

Several workers previously attempted karyotypic analysis of ferns and concluded that the high chromosome numbers that characterize extant fern genera reflect high polyploidy. An examination of fern karyotypic data suggests that observed differences in total length and arm length ratio between chromosomes and chromosome groups are subject to many errors. The possibility of such errors suggests that karyotypic analysis in ferns is a dubious practice. Graphic and statistical methods of analysis were applied to karyological data. Unreasonable inferences were made previously from the karyotypic data. Fern evolution at the generic level probably occurred from ancestors that had essentially the same high chromosome numbers observed in living ferns. [Species analyzed included Asplenium incisum, A. varians Camptosorus sibiricus, Diplazium esculentum, Hymenophyllum barbatum, Isoetes asiatica, Osmunda japonica, Osmundastrum cinnamomeum var. fokiemse, O. claytonianum, Plemasium, banksiifolium and Pteris wallichiana.].