WHITTIER, DEAN P. Department of Biology, Vanderbilt University, Nashville, TN 37235-1565. - Apogamy in Psilotum and Tmesipteris.
Gametophytes of Psilotum and Tmesipteris grow slowly in
axenic culture on a nutrient medium containing minerals and 0.5%
glucose. Gametophytes grown in the dark have the typical cylindrical
shape and bear antheridia and archegonia. If these gametophytes are
grown in the light, they will form apogamous aerial stems from their
apices. The apogamous stems have the expected morphology for aerial
stems of the two genera. The stems of Psilotum have vascular
tissue, stomata, and enations and those of Tmesipteris differ
only in having microphylls instead of enations. If the apogamous stems
of Psilotum are moved into the dark, their development will
shift to that of rhizomes. If the nutrient medium is supplemented with
6-benzylaminopurine, gametophytes will form apogamous rhizomes in the
dark. It would appear that the presence or absence of light determines
whether the apogamous developments in Psilotum are aerial stems
or rhizomes.
Key words: apogamy, Psilotum, Tmesipteris