and black, and arose, often in a very short time on the roofs of houses, on clothes, on the veils and neck handkerchiefs of women, on various household utensils, on the meat in larders, &c. A historian, who speaks also of blood-rain[434], recounts that they could not be got rid of in less than ten or twelve days, and that they frequently occurred in closed chests, on linen and on articles of clothing[435]. Much information is not to be expected from the researches of the naturalists of those times, but there is no doubt that what is described was some one or more kinds of mould[436], inasmuch as the whole phenomenon evidently corresponds with modern observations[437]. Scientific physicians of the sixteenth century, among whom the naturalist George Agricola, who was born in 1494, and died in 1555, ought especially to be mentioned, recognised, even then, these spots as lichens, and without seeking to account for them by supernatural agencies, or lending credence to popular superstition, they gave them their just interpretation as indications of extensive disease[438]. Should the too bold notion of Nees v. Esenbeck, that fungi of the most minute forms have their origin in the higher regions of the firmament, and descending to the surface of the earth, produce spots and stains, be confirmed, which is not yet the case, these “signacula” would have a much more important connexion with epidemics than can be otherwise conceded to them; for though it be highly probable that they have their origin only in the dissemination of germs in the lower strata of the atmosphere, it must yet be granted, that if they appear over a considerable space, and during a long time, as at the commencement of the sixteenth century, the causes favouring their generation and spread, must be ranked among those of an extraordinary kind, and on this very account may exercise an influence over human organism, as was then evident.