Chemical changes in preserved animal and vegetable substances afford suitable food for the Penicillia mould, if indeed they are not the immediate cause of these changes. The threads rising from the mycelium of these moulds terminate in bundles of branchlets carrying at their summits strings of spores, like necklaces of small beads collected into bunches like tassels, white, yellowish, blue or red according to their age or kind. Figure 34 represents various species of Mucedines, in which _c_ is the Penicillium armeniacum, and _f_ is a spore of Helminthosporium Hoffmanni; all are magnified. Different species of the Penicillia form the blue and brick-red moulds on cheese, and the greenish and grey moulds on jam and preserved fruit. They appear as dry rot, as orange coloured spots on long kept potatoes, as mildew on cloth, silk, sugar, meat, and even on weather-beaten window glass. They can exist in metallic and poisonous solutions by decomposing the chemical combination, rejecting the metal or poison, and living on whatever nutriment may be found in the remainder. Like the larger fungi, these minute plants are sometimes poisonous; the fatal effects occasionally produced by sausages and spoilt meat are supposed to be owing to poisonous moulds. The Mucedines conform to the law prevailing in other low organizations of having their species widely distributed. The Penicillium glaucum is found in all countries, especially in the vicinity of man; it inevitably appears in all saccharine substances, and, according to M. Fries, it is met with alike in the alps of Lapland and in the oasis of Jupiter Ammon in the Lybian desert, an example which has no parallel in the geographical distribution of the higher plants.[56] Ferment, that is to say, the yeast plant, is a peculiar condition of certain fungi, including the present species, and is capable of unlimited propagation. [Illustration: Fig. 34. Mucedines:—_a_, Aspergillus glaucus; _b_, Aspergillus dubius; _c_, Penicillium armeniacum; _d_, Sepedonium mycophilum; _e_, Helminthosporium nodosum; _f_, Helminthosporium Hoffmanni, spore; _g_, Zygodesmus fuscus.]