Wednesday, May 06, 2015

Bare-bones flowers

Eelgrass is not a seaweed, but a perennial flowering plant, related to the land-based grasses. In spring and summer, the plants send out long, stiff stems, bearing clusters of flowers. "Relatively inconspicuous," Kozloff says; an outright understatement. 

You'd never seen them? Nor had I. I'd found the unripe seeds; rows of yellow-green buttons along the blades, but no flowers. Until now. The lonely eelgrass plant I found last week is loaded with them, tiny male and female flowers in separate rows, half hidden between the blades.

They don't exactly look like my preconceived idea of flowers, but the essentials are there.

Zostera marina; female flower styles, half covered by a sheath. A few developing seeds on a lower blade. And the yellowish, stiff stem at lower right. The blades of eelgrass are 4 mm. wide at this point.

The female flower is little more than a two-pronged tube (the style) with an ovary beneath. It captures floating pollen threads, and then bends down against the blade to produce its fruit. Each fruit contains one seed.

Another row of female flowers, one tangled in pollen.

The male flower grows on the same plant, but on different blades. It does look a bit more "flowery"; it is like a thick, cupped petal a few millimetres tall, and releases pollen at the tip.

Three blades of eelgrass, one with a style and pollen, and the rear one with the anther, which produced the pollen.

The male flowers depend on water currents to carry the pollen threads to the styles; no other pollinators are needed. The stems are light and float to the surface, which keeps all the flowers more or less at the same depth and exposed to sunlight. The seeds, once they mature, are heavy, and drop out of the sheath to the ground beneath. There they may take root, or be eaten by birds and fish, and carried, undigested, to new meadows.

I've noticed that the hermit crabs eat everything that grows on the eelgrass, except the flowers and seeds; these they leave strictly alone.

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