Stachybotrys conidia

Stachybotrys is a genus of soil fungi in the natural environment. It is commonly found indoors on wet cellulose-based materials, such as drywall, ceiling tiles, jute, wicker, straw baskets, and paper materials. Some consider Stachybotrys conidia to be allergenic although little is known. Some strains of this genus produce mycotoxins. 

Stachybotrys conidia are generally ovoid or ellipsoidal, dark brown to black, single-celled and 7–12 µm long. The spore surface is warty and has a slimy coating.