Prior to Leeuwenhoek’s description of microorganisms, the Englishman Robert Hooke had released his book Micrographia. Within this book (Observation XX ) Hooke describes some mould found on a book cover:
But, first, I must premise a short description of this Specimen, which I have added of this Tribe, in the first Figure of the XII. Scheme, which is nothing else but the appearance of a small white spot of hairy mould, multitudes of which I found to bespeck & whiten over the red covers of a small book, which, it seems, were of Sheeps skin, that being more apt to gather mould, even in a dry and clean room, then other leathers. These spots appear’d, through a good Microscope, to be a very pretty shap’d Vegetative body, which, from almost the same part of the Leather, shot out multitudes of small long cylindrical and transparent stalks, not exactly streight, but a little bended with the weight of a round and white knob that grew on the top of each of them; many of these knobs I observ’d to be very round, and of a smooth surface, such as A, A, &c. others smooth likewise, but a little oblong, as B; several of them a little broken, or cloven with chops at the top, as C; others flitter’d as ’twere, or flown all to pieces, as D, D. The whole substance of these pretty bodies was of a very tender constitution, much like the substance of the softer kind of common white Mushroms, for by touching them with a Pin, I found them to be brused and torn; they seem’d each of them to have a distinct root of their own; for though they grew neer together in a cluster, yet I could perceive each stem to rise out of a distinct part or pore of the Leather; some of these were small and short, as seeming to have been but newly sprung up, of these the balls were for the most part round, others were bigger, and taller, as being perhaps of a longer growth, and of these, for the most part, the heads were broken, and some much wasted, as E; what these heads contain’d I could not perceive; whether they were knobs and flowers, or seed cases, I am not able to say, but they seem’d most likely to be of the same nature with those that grow on Mushroms, which they did, some of them, not a little resemble.”
Author Howard Gest brings forward the case (see this article) that Hooke was in fact the first to observe a micro-organism, rather than Leeuwenhoek.