A NEW TYPE OF APOGAMY IN FERNS

Summary Studies on apogamous members of the Asplenium aeihiopicum complex in Africa have shown a marked departure of cytological behaviour from that previously known in apogamous ferns. The sporangial development is characterized by all sporangia producing sixteen spore mother cells each showing complete asynapsis at diakinesis with either 288 or 330–357 chromosomes. The first meiotic division ends in a restitution nucleus which then divides regularly to produce diads of diplospores. This abbreviated meiosis is compared with the cytological phenomena accompanying apogamy in other ferns and with a similar division process known from apomictic Angiosperms. Evidence is presented from the literature which indicates that a similar abbreviated meiosis may accompany apogamy in the Hymenophyllaceae. Little new evidence on either the causal aspect of apogamy or the possible origin of the apogamous forms within the A. aethiopicum complex can be adduced at present.