Galls on leaf of rose. The location of a parasite is often marked by swellings of peculiar and fantastic or beautiful forms (galls) that grow on leaves and stems.
GalleriesDisease and Pest Management
John Merle Coulter, C.R. Barnes and H.C. Cowles, A Textbook of Botany for Colleges and Universities (New York:American Book Company, 1910) 384