Dark Pu-erh (also spelled Pu'er) tea is produced in China using Aspergillus foetidus var. acidus to ferment the tea leaves. Unlike Aspergillus niger, which it resembles, A. acidus does not contain mycotoxins ochratoxin A and fumonisins B2 and B4. A. acids was grown on an agar plate and the sporangia were photographed under a dissecting microscope. Image width: 2306 micrometers. Magnification: 43.4x if the image is printed 10 cm wide.