10 books
German Hymnology (Classic Reprint)
Flora of Pennsylvania (Classic Reprint)
The Pennsylvania-German in the Field of the Natural Sciences, Vol. 6 (Classic Reprint)
Catalogue of the Bryophyta (Hepatics, Anthocerotes and Mosses) and Pteridophyta (Ferns and Fern-Allies) Found in Pennsylvania (Classic Reprint)
A List of the Grasses of Pennsylvania... - Primary Source Edition
Catalogue of the Bryophyta and Pteridophyta
A List Of The Grasses Of Pennsylvania
Synopsis of the Flora of Colorado
Synopsis of the Flora of Colorado (1874)
Flora of Pennsylvania