There are many additional species of smut fungi in the order Ustilaginales, particularly smuts that attack grasses. Some of these include corn smut, oat smut and wheat smut. There are even smuts that attack weedy grasses such as Johnson grass and Bermuda grass. These fungi typically infect the fruiting inflorescence region with sooty masses of spores.
Close-up view of Wolffia sample from a lake in Minnesota: Wolffia borealis (1) and W. columbiana (2). The average length of each Wolffia plant body is 1.0 mm (1/25th of an inch). Magnification 15x.
Flowering Wolffia columbiana: On individual plants, maturation of minute flowers within the dorsal floral cavity is protogynous: The stigma is receptive before the anther releases pollen. When the stima is receptive a droplet of stigmatic fluid is secreted. By the time the anther has split open and released its pollen, the stgma has already dried and withered. This strategy favors cross pollination between different plants. Magnification 20x.
Protogynous Wolffia columbiana: The stigma has already dried and withered. The anther has not yet released its pollen grains. Magnification 40x.
Floral "orgasm" of Wolffia columbiana: A mass of pollen grains have been released from a dehiscent anther within the floral cavity. The stigma has already shriveled up and is no longer receptive. Magnification 25x.