of Apogamy and Apospory.
1, Preliminary the Cytology of Apogamy and Apospory. Note on Apogamy." By J. B. Farmer, F.E.S., J. E. S. Moore, and Miss L. Digby. Received March 24, Bead March 26,
The phenomena of apogamy and apospory have always been regarded "short cuts" in the life history of ferns, and the fact that either
other, without the intervention of oosphere or spore respectively, has
been taken to indicate that the gametophyte and sporophyte are homologous phases in the life histories of these plants. But since the cytology of the two generations has been carefully studied, it has become recognised that the prothallial generation is composed of cells, the nuclei of which possess only half the number of chromosomes that are characteristic of the alternate sporophyte generation.
In normal cases the doubling of the number of the chromosomes effected during the transition of the
gametophyte to sporophyte by
the addition of the chromosomes belonging to the spermatozoid to
those of the oosphere,
retained until they
once more become reduced to one half in the formation of the spores that introduce again the gametophyte stage of the life-cycle. It is
obviously therefore of considerable theoretical
known as apospory and facts of apogamy that we are
here concerned, the details relating to apospory being reserved for a future communication.
Certain species of nephrodium
to produce prothallia on
N. pseudo-mas, var. polydactylum) which the apogamous formation
normal instead of rare occurrence.*
kindness of Dr.