A Walk Through Time

Sowing And Reaping

280 Million Years Ago

Profound changes in climate, glaciation and finally widespread desertification are linked to the tectonic assembly of the supercontinent Pangaea. Conifers, gingkos and cycads — naked-seed, "cone-bearing" trees — and dry-tolerant spore ferns replace the dying lush Carboniferous forests. Wind carries pollen from tree to tree, a common pollination method before some animals begin to provide the service.

Cycads grow well in soils extremely low in nitrogen. Cyanobacteria, living in the roots where they induce a special layer of tissue, convert nitrogen from the air to a form usable by the cycad.

The giant ferns did not make it through the climate change; smaller close relatives did. (Photography by Lois Brynes)

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