"Fungi and fungi-like eukaryotes are commonly associated with plants where they adopt a variety of roles ranging from ones of mutual benefit (e.g., nutrient acquisition via mycorrhizae in roots) to others that are exploitative to varying degrees (e.g., parasites). These associations are of great evolutionary importance, but although they are known to be ancient direct evidence from the fossil record is scarce. My research has shown that there exists a large, novel and as yet largely untapped source of information on early fossil fungi and fungi-like eukaryotes. This takes the form of collections of petrified plants made during the 19th and 20th centuries. Petrifactions preserve the anatomy of fossil plants in exquisite detail, which was the original focus of their collection and study, but it is now recognised that they also contain the well-preserved remains of microscopic eukaryote symbionts. Much material exists in a prepared form that is suitable for analysis (i.e., petrographic thin sections). My project will explore and develop this resource. I will undertake the first large scale systematic survey of an historic slide collection of petrified plants to document their microscopic eukaryotes. This will be based on the large and comprehensive collections at The Natural History Museum, London. I will be trained in state of the art imaging methods and phylogenetic analysis to enable me to document the diversity of the symbionts and to determine their affinities to key living groups. My overarching goal is to reveal and to understand the significance of microorganism/plant associations in the early development of land ecosystems."