Cytological problems in Lycopodium sens. lat

Homosporous pteridophytes differ from seed plants most strikingly in their potential ability to produce completely homozygous offspring from a single haploid spore. The Lycopodiaceae share this characteristic with the ferns, but differ from them in the absence of apogamy and in the relatively high frequency of allohomoploid nothospeciation in certain genera. Determining chromosome numbers in this family is often difficult, and discrepancies are found in published accounts. Evidence in support of a base number of 11 is presented. Allohomoploid nothospeciation is described involving four species of Diphasiastrum. A table giving the published chromosome numbers in Lycopodium sens. lat. is included.