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Underground Botany: Hidden Flowers and Buried Fruits

16 Jul

What do Innocence, Blue Maidencane Grass, Bog White Violet, and Beach-Peanut have in common? Hint: Look at the title of the post. They all have “funny” flowers and fruits doing things you don’t expect where you don’t expect them.

Houstonia procumbens 2

Innocence

Innocence (Hedyotis procumbens) is a petite member of the Coffee Family (Rubiaceae) related to the Bluets familiar to readers with more northern exposures. In South Florida the species turns up on sun-baked dry sugar sand in scrub or near-scrub habitats. The small white flowers often appear to spawn directly on the sand, as the vegetative plant body is low, trailing, and frequently more or less covered with sand. After flowering, the flower stalk bends earthward burying the developing fruit protectively for subterranean maturation. To be speculative, it looks like ants might disperse the resulting fruits and seeds. And there is more to the story: Innocence is not so innocent. In addition to the showy flowers, it hides secret inconspicuous flowers underground. These either self-pollinate or do not require pollination, and they produce fruits without seeing light of day. Such flowers are a “back-up” on the sexual process and are called cleistogamous (kleist-OG-ah-mus) flowers. Cleistogamous comes from Greek for, roughly speaking, “hidden husband.”

The most famous owners of cleistogamous flowers are violets, and our native Bog White Violet (Viola lanceolata) is no exception. Look for the hidden flowers or the resulting fruits near the base of the plant.

Bog White Violet

Bog White Violet

A more surprising case is the grass Blue Maidencane (Amphicarpum muhlenbergianum, see http://www.floridagrasses.org). Amphicarpum translates as “fruits on both sides“, in this case, both sides of the ground surface. In addition to normal (chasmogamous) flowers and fruits in the sunshine, cleistogamous flowers in the rhizome make buried fruits. John and I saw these first and most easily in an area rooted up by feral hogs.

Blue Maidencane

Blue Maidencane

Blue Maidencane Buried Fruit

Blue Maidencane Buried Fruit

Buried fruits are hidden from some menace, and what could be more menacing than clinging to life on Florida seashores and seaside dunes. You can guess now how Beach-Peanut (Okenia hypogaea) got its name. Not for being a type of goober. The Beach-Peanut is no legume, but rather a member of the Four O’Clock Family (Nyctaginaceae), as you might guess from its vibrant floral display. The prettiest flower on the beach buries its fruits in the sand on a downward peg potentially mistaken for a root. It too produces cleistogamous flowers, but the relative roles of the cleistogamous flowers and showy flowers remain poorly studied.

Beach-Peanut

Beach-Peanut

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