Junghuhnia japonica is a species of poroid crust fungus in the family Steccherinaceae. The type specimen was collected in à Âkuchi, Japan, growing on a rotting log of Castanopsis. The fungus is only known from the type locality. Its cylindric spores measure 4âÂÂ5 by 2âÂÂ2.4 üm and are smooth and hyaline. J. japonica has two types of cystidia. One type is thick walled and heavily encrusted, measuring 40âÂÂ70 by 9âÂÂ15 üm. The other type is tubular, smooth, and thin walled, measuring 20âÂÂ35 by 4âÂÂ8 üm. The latter type, which have an oily or granular appearance under the microscope, are known as gloeocystidia.
The fungus was described as new to science in 1999 by mycologists Maria Núñez & Leif Ryvarden. J. japonica is similar in morphology to J. luteoalba but that species has narrower spores and lacks gloeocystidia.