Evolution and survival
When he speaks of ferns, Kuo always takes the trouble to go back to the genesis of our world. The earth came into being 4.5 billion years ago. Woodlands did not appear until 400 million years ago. Ferns were the most dominant plants at that time, and the forests were made up of tree ferns. Spermatophytes (seed-bearing plants) arrived on the scene 200 million years ago. The first spermatophytes were conifers, which are gymnosperms (plants with exposed seeds), and it was they that replaced ferns as the dominant woodland species. Subsequently, 100 million years ago, flowering plants, which are angiosperms (plants with enclosed seeds), gained preeminence. Since then, broad-leaved angiosperms have dominated our woodlands.
But ferns should not be underestimated. They have been busy surviving in the most unlikely places, such as rocky precipices and broken terrains, where the slightest amount of soil will enable them to live. In dry habitats some ferns preserve moisture by shedding their leaves.
Standing in the walkway outside the NTU Herbarium, Kuo directs our attention to a tuft of rock-ginger fern (Pseudodrynaria coronans) growing on a tree. “It’s an epiphyte, not a parasite. This means that it has to find ways itself to acquire the moisture and nutrients it needs, which is why the fern encircles the tree trunk. It’s like a roadblock: whatever flows down the outside of the trunk will have to leave behind something valuable for the fern,” Kuo explains with a smile.
Next, turning to a knee-high fern, Bolbitis subcordata, Kuo flips over its fronds and points out the “adventitious buds” at the tips. When the fronds are long enough to touch the ground, these buds will drop onto the soil and grow into new plants. In adverse environments, B. subcordata is able to use this mechanism to relocate to habitats that are more hospitable.
Tamariskoid spikemoss (Selaginella tamariscina), on the other hand, copes with drought by changing its face. When the weather is dry, the fronds will curl up, looking withered and dead, only to unfurl again when it rains.
If you wish to learn more about ferns, Kuo recommends beginning with those that grow on trees and rocky surfaces. Relative newcomers in ferns’ evolutionary history, they demonstrate a strong will to survive in hostile environments.
Southern maidenhair fern (Adiantum capillus-veneris)
Turnip fern (Angiopteris lygodiifolia)
Bird’s nest fern (Asplenium nidus)