The Use of Green-Stained Wood Caused by the Fungus Chlorociboria in Intarsia1 Masterpieces from the 15th Century

Green-stained wood from one of the intarsia panels of the Gubbio studiolo, (Italy, 15th century, in the collection of The Metropolitan Museum of Art, New York) and an intarsia panel made by Fra Giovanni da Verona, (Italy, around 1500, in the collection of the Historical Museum of Amsterdam), were sectioned and examined by light, scanning and transmission electron microscopy and energy dispersive X-ray microanalyses. Sections of green-stained wood from the intarsia panels contained evidence of fungal hyphae in vessels, fibers and parenchyma cells. Colored deposits that were yellowish-orange or green were found to be extensive in ray parenchyma cells and in vessels and fibers adjacent to the ray parenchyma. The staining pattern within the wood was not uniformly distributed but concentrated in areas where fungal hyphae were present. The woods were identified as Populus sp. No fungi were evident in samples obtained from other woods (Quercus sp. and Juglans sp.) adjacent to the green-colored wood within the artwork. X-ray microanalyses of the green wood showed no evidence of high concentrations of metal ions that would be present if inorganic dyes were used. Transmission electron microscopy showed the ultrastructural distribution of fungal hyphae and pigmented substances within the woody cells as well as an erosion of the secondary wall layers in some cells. A comparative study of recently collected green-stained wood caused by the fungus Chlorociboria (syn. Chlorosplenium), showed the micromorphology of fungal colonization and pigment deposition was identical to the patterns observed in the green wood of the 500 year old intarsia panels.