John Ray FRS was a Christian English naturalist widely regarded as one of the earliest of the English parson-naturalists. Until 1670, he wrote his name as John Wray. From then on, he used 'Ray', after "having ascertained that such had been the practice of his family before him". He published important works on botany, zoology, and natural theology. His classification of plants in his Historia Plantarum, was an important step towards modern taxonomy. Ray rejected the system of dichotomous division by which species were classified according to a pre-conceived, either/or type system, and instead classified plants according to similarities and differences that emerged from observation. He was among the first to attempt a biological definition for the concept of species, as "as a group of morphologically similar organisms arising from a common ancestor". Another significant contribution to taxonomy was his division of plants into those with two seedling leaves (dicotyledons) or only one (monocotyledons), a division used in taxonomy today.