The haploid-diploid cycle manifests itself in ferns
in big diploid sporophytes and small haploid gametophytes

I remember that from high school.

except in some populations hit by the Ice Ages.

What happened to them?
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)