The biologist Dr. Philippe Clerc is a specialist of cryptogamic plants (those which reproduce with spores, without seeds or flowers), such as lichens. + plus As a systematist and taxonomist, he is co-director of the herbarium at the Conservatory and Botanical Garden of the city of Geneva. Philippe Clerc is also a professor and researcher at the University of Geneva. The regional and Swiss flora of lichens are part of his research interests, as well as Usnea (a genus of mostly pale, grayish-green fruticose lichens) in Micronesia and North and South America. Clerc considers symbiosis rather than competition to be one of the key biological processes on Earth.