Underwater reproduction

I thought some of you might be interested to see the miniscule (2-3mm) underwater flower of horned pondweed Zannichellia palustris, found yesterday while doing some botanical recording on the way back from Spalding. The 'flower' actually consists of four peltate stigmas, which are colourless and formed from a single layer of cells. In time these will produce the more obvious fruits that give this pondweed its name.




We also found a very extensive area of clustered stonewort Tolypella glomerata in a shallow ditch running south from the River Welland. This had many reproductive structures, which are the orange ovals in the tangled fertile whorls. This is a nationally scarce species of water with a high pH, ranging from semi-permanent puddles, through to ditches, pools and pits. Where sites dry up in the summer, but are flooded in winter, the plants germinate in autumn and overwinter, producing ripe oospores as early as May or June.