SynopsisThe fixation or loss of somatic mutations is considered in terms of apical initials and apical meristem organisation. Two general kinds of apical meristems are mathematically modelled: structured and stochastic. Structured apices have permanent apical initials whereas stochastic apices are more dynamic systems with apical initials randomly selected from an apical cell pool. With regard to neutral or completely recessive mutations, the probabilities of fixation or loss of mutations are identical for both structured and stochastic apices. For mutations which have a disadvantageous effect in heterozygous cells, diplontic selection occurs. In such cases, stochastic apices are purged of mutations more effectively than structured apices.The majority of ferns have highly structured apices based upon single apical cells. Since such apices are the least able to be purged of disadvantages mutations, mutational load may be a significant aspect of the biology of these plants. Ferns that exhibit primarily asexual reproduction (either apogamy or vegetative reproduction) may also exhibit strong linkage disequilibrium between loci due to mutation.