Though they fall in flurries just like snow flakes in the wind, they are not cold and do not melt.

They are the seeds of certain poplars (like the Populus Alba that grows plentiful along the banks of the Arno River). The cottony filaments help the seeds catch a ride on air currents and disperse widely, giving them a better chance to grow away from the mother plant, where they won't have to compete with it for light and nourishment. This particular tree, however, grows in an area sheltered from the wind and had little opportunity to send its "children" off into the blue. Most of them collected on the ground or got caught on the grasses lining the path.