Aspergillus foetidus var. acidus is a fungus which is used in China to produce dark Pu-erh tea, also spelled as Pu'er tea, in Yunnan Province. Unlike Aspergillus niger, which it resembles, A. acidus does not contain mycotoxins ochratoxin A and fumonisins B2 and B4. Tea production is a lengthy process: for example, a ripened Pu'er produced in early 2004 was pressed in the winter of 2004/2005, and appeared on the market between late 2005 and early 2006. Images of the spores were obtained by SEM after new fungus was grown on an agar nutrient plate from marketed Pu-erh tea. The sporangia were lightly touched with a glass cover slip pre-coated with gold and the spores adhering to the cover slip were coated with gold and were examined by SEM. Enhanced SEM. Image width: 18.28 micrometers. Magnification: 5470x if the image is printed 10 cm wide.