Ludwig Schkuhr, of Wittenberg, an eminent cryptogamist; Professor and Medical Counselor Heinrich Adolph Schrader, of Göttingen; Kurt Sprengel, professor of medicine and botanist at Halle; and Prof. Olof Swartz, one of Linnæus's most eminent pupils. Among the twenty-eight home correspondents mentioned by Muhlenberg in the preface to his catalogue are the Rev. Christian Denke, of Nazareth, Pa., the Rev. Samuel Kramph, of North Carolina, the Moravian bishop Jacob Van Vleck, and Dr. Christopher Müller, of Harmony, Pa. One of the most valued was Dr. Baldwin, of South Carolina, and Muhlenberg's letters to him have been published by William Darlington, in a volume entitled Baldwiniana. All or nearly all these correspondents were entertained by him in his home at Lancaster, which was open to all students of plants, and was usually visited by them when they came to Philadelphia. Alexander von Humboldt and Aimé Bonpland sought him there on their return from their long sojourn in Spanish America; and Humboldt's letter acknowledging his hospitality is the last which that master in science wrote in America.
Learned societies and institutions likewise covered him with their honors. The University of Pennsylvania gave him the degree of Master of Arts in 1780; Princeton College, that of Doctor of Divinity in 1787. He was elected a member of the American Philosophical Society on January 22, 1785, along with Joseph Priestley and James Madison. Of other societies he received diplomas: from the Imperial Academy of Erlangen, 1791; the Society of Friends of Natural History, Berlin, 1798; the Westphalian Natural History Society, 1798; the Phytographic Society of Göttingen, 1802; the Physical Society of Göttingen, 1802; the Linnæan Society of Philadelphia, 1809; the Academy of Natural Sciences of Philadelphia, 1814; the Society for the Promotion of the Useful Arts, Albany, N. Y., 1815; the Physiographical Society of Lund, Sweden, 1815; and the New York Historical Society, April 12, 1815, not quite six weeks before his death.
Introducing the description of a Muhlenbergia in the second volume of his work on the Grasses, Prof. Schreber wrote: "The genus of which this remarkable grass is on account of its beauty and of the particularly curious structure of its organs of fructification one of the most notable species, received its name from me when I published the new edition of the Genera Plantarum of the honored Linnæus, after my most revered friend Dr. Heinrich Muhlenberg, evangelical preacher at Lancaster, Pennsylvania, and President of Franklin College there, and also an eminent member of many learned societies; who has, through the discovery of numerous new species and in other ways, rendered immortal service to the natural history of North America, and especially to the knowledge of the plants of Pennsylvania and the other United States."