Sclerotinia sclerotiorum

This fungal species is easily identified. By day 7 it will have covered the entire plate, unless there is competitive inhibition by another fungus. The center will be mostly flat with little mycelium, and where there is resistance (either a seed or the edge of the plate) you will see white mycelium, somewhat tufted in nature. Scattered around the plate you will see sclerotia[1], sometimes roridous[2], which are very hard and black, less than a centimeter long (usually ~0.5cm) and lumpy, usually rounded. They are irregular in size and texture. The sclerotia will generally start off grey in coloration around day 5, and then turn a black color by day 7. When viewed from the back of the agar, the coloration starts fairly white, but becomes darker grey/brown with age.