Thanks to Janice for sending me emails from bryonet. One mentioned
the term "heterosporangy" as applying to the sporangium. This seems
to be a much better term to use for "heterosporous" fern allies
and seed plants - you don't have to worry about the "size" of
the spores.
Also I did a bit of sleuthing in some bryology books, and found
some fascinating facts: in the 1940's two heterosporous moss
genera from the tropics were reported, the spore mother cell
producing two large green spores (--> female gametophytes) and
two small yellow spores (--> male gametophytes). In addition,
another uncovered fact was that environmental influences can
induce spores to "change sex", so to speak, after they have
been formed.
It seems to me that we should teach the life cycles as
follows (for Plantae): heterospory for spores "sexually
distinct" which would include bryophytes and hepatophytes,
ferns and fern allies in which there is only one kind of
sporangium. "Heterosporangy" for the seed plants and those
fern allies with different sporangia. Mosses would never be
included in this. Que pensez-vous? -Nan
