Originally, cultivation was unreliable as mushroom growers would watch for good flushes of mushrooms in fields before digging up the mycelium and replanting them in beds of composted manure or inoculating 'bricks' of compressed litter, loam, and manure. Spawn collected this way contained pathogens and crops commonly would be infected, or not grow at all.[15] In 1893, sterilized, or pure culture, spawn was discovered and produced by the Pasteur Institute in Paris, for cultivation on composted horse manure.[16]