IV. The relationship of micro-organisms to the decay of stone - Part XIII.—On a new type of mucilaginous material, Luteic acid, produced from Glucose by Penicillium luteum Zukal

ThePenicillium luteum —P. purpurogenum group of species ofPenicillium described by Thom (1915), contains a number of species and strains, with a strain ofP. luteum Zukal, at the one end of the series andP. purpurogenum Stoll, at the other end. The strain ofP. luteum Zukal, which occupies one end of this series, “ produces ascospores freely in all the media used and conidia very sparingly. In the actively growing culture the dominant shades of colour are yellow with tardy appearance of red.”P. purpurogenum Stoll, at the other end of the series, “ produces only conidia, in which yellow shows transiently while red colours in mycelium and substratum are abundant.” “ The production of yellow in the surface growth at some period of colony development or under some cultural conditions is typical for the group. This may be dominant, transient, or almost lacking, yet it is not difficult to demonstrate in the organisms studied. Coincident with the change of colour in the surface or aerial growth we find at theluteum end of the series that yellow to orange shades predominate in the substratum. These slowly or but partially change to red as the colonies become old. In the forms producing conidia only, yellow or orange tones still appear in the young colony. The change to red is slow and only partial in some forms, but towards thepurpurogenum end of the series the yellow colours are reduced to but transient appearances, replaced quickly and almost completely by red.” (The quotations are from Thom’s paper quoted above.)