The pteridophyte collection ranks fourth in the nation in size and includes more than 106,000 specimens of ferns and fern allies, including 373 types. The collection is worldwide in scope but has a strong concentration in tropical America. The Ferns and Fern Allies of Guatemala and Pteridophyta of Peru were based primarily on our holdings. Central American and Mexican collections include the outstanding material of Standley, Steyermark, Molina and L. O. Williams (Guatemala), Matuda, Ringle and Purpus (Mexico), Molina, Williams, Shimek (Nicaragua), and Brenes and Austin Smith (Costa Rica). South American material includes specimens from J. F. Macbride, Mexia, Killip and Smith, and both Carlos and José Schunke (Peru), Cuatrecasas (Colombia), Steyermark and Llewelyn Williams (Venezuela), Acosta Solis (Ecuador), Buchtien and Steinbach (Bolivia), and Brade (Brazil). Although Old World specimens are not especially numerous, they include valuable collections of Blanchard (Africa), Boivin and Humblot (Réunion, Madagascar) and Zenker (Cameroon).