THE surface of many fungal spores, including those of some members of the ascomycetes, basidiomycetes and deuteromycetes, is covered by a thin layer of regularly arranged ‘rodlets’1–3. The limited data available on their chemical nature suggest that these rodlets are composed largely of protein with some polysaccharide4–5 Functions suggested for the rodlet layer have included water repellency4 and protection against dehydration2 but little experimental evidence has been available. We report here such evidence, based on a study of a mutant of Neurospora crassa that differs from the wild type in that its asexual spores (conidia) are both easily wetted and do not disperse readily in air currents. The conidia of the mutant, unlike those of the wild type, lack rodlets on their surface.