Final answer:
Mary Matossian linked the wet and rainy weather conditions in fourteenth-century Europe to the prevalence of the fungus Claviceps purpurea on rye, causing outbreaks of ergotism due to the production of ergot toxin.
Step-by-step explanation:
According to Mary Matossian, there was a significant relationship between weather conditions and the occurrence of ergot of rye in Europe. The rainy, wet conditions prevalent during the fourteenth century created ideal circumstances for the fungus Claviceps purpurea, which grows on rye and related grains, to produce the mycotoxin known as ergot toxin. This ergot toxin was responsible for outbreaks of ergotism in Europe, a disease that could lead to severe health consequences including gangrenous ergotism and convulsive ergotism. The heavy summer rains and colder weather patterns not only prevented grain from ripening properly but also promoted the growth of this dangerous fungus, demonstrating a clear link between climatic conditions and the spread of disease through agricultural staples like rye.