Moses Marshall (November 30, 1758–October 1, 1813), a Quaker physician and botanist in Chester County, Pennsylvania, assisted his uncle, Humphry Marshall, with a variety of botanical pursuits, including collecting and identifying American plants and seeds and distributing them to European and American correspondents.
Although Moses Marshall never received a medical degree, his contemporaries invariably referred to him as "Dr. Marshall." He studied with the physician Nicholas Way in Wilmington, Delaware from 1776 to 1779, and with Benjamin Rush and William Shippen at the University of Pennsylvania during the winter of 1779–1780. After practicing medicine and apothecary for a few years, Marshall joined the household of his father's elder brother, the botanist and plant dealer Humphry Marshall, in April 1784. Marshall gained extensive knowledge of American plants and developed expertise as a practical botanist while assisting with the botanic garden that his uncle was developing at his rural estate thirty miles west of Philadelphia. He further assisted his uncle by managing some of his correspondence with clients in America and Europe and by helping to fill their requests for seeds and plants. Two letter-books containing Marshall's responses to inquiries from clients during the years 1791 and 1793 are preserved at the University of Michigan. According to early biographical accounts, Marshall also contributed to Arbustum Americanum: The American Grove (1785), his uncle's catalog of forest trees and shrubs indigenous to the thirteen States, although the book was presumably already well advanced by the time Moses arrived on the scene.
According to Marshall's friend William Darlington, his uncle "greatly extended his operations" as a result of Moses's assistance (view text). Humphry Marshall solicited employment for his nephew among London's learned societies, informing Sir Joseph Banks in 1786, "As my nephew is well versed in the knowledge of Botany, and would gladly be employed in researches in that line...if the Royal Society should have a mind to employ any person, on this side the water, for such purposes, he would be willing to serve them" (view text). In 1791 Banks sent Moses a list of plants desired for the botanic garden at Kew in England, drawn up by the director, William Aiton (1731–1793). In the same year Marshall received another long list of desired plants from the German botanist Johann Jakob Reichard (1743–1782). Marshall also filled orders from commercial firms in Great Britain, such as Grimwood, Hudson, and Barrit, and supplied information and plant materials to American gentleman gardeners, such as James M. Walton in Charleston, South Carolina, and William Hamilton, whose estate on the outskirts of Philadelphia, The Woodlands, Marshall occasionally visited ().
Through his correspondents, Marshall gained access to the most recent books on botany. In May 1788, for example, he wrote to the Quaker physician John Coakley Lettsom (1744–1815) in London asking for the latest edition of Carl Linnaeus's Genera Plantarum (7th ed., 1778) as well as the Supplementum Plantarum (1782) of Carl Linnaeus the Younger (1741–1783). In exchange, Marshall acquainted Lettsom with an unusual American plant, which he described according to Linnaean taxonomy and illustrated with a drawing of his dissection. He offered to name the plant Lettsomia in Lettsom's honor, should it prove to be a new genus, which it did not (). Eager to initiate a correspondence with Marshall, the Lutheran clergyman and botanist Gotthilf Henry Ernest Muhlenberg (1753–1815) sent him the latest edition of Linnaeus's Materia Medica (6th ed., 1787) in 1790 and offered to loan examples from the "great many botanical writings" in his private library in Lancaster, Pennsylvania (view text). Two years later, Muhlenberg informed Marshall that the new edition of Linnaeus's Genera Plantarum (2 vols., 1789–1791) included Marshallia, a previously undescribed plant named in Marshall's honor (view text) [Fig. 1].
As early as 1784 Marshall had begun trekking to outlying wilderness areas on his uncle's business, searching for plants and seeds to propagate in the botanic garden and to sell or exchange with European correspondents (view text). In a letter of 1785 the elder Marshall sought Benjamin Franklin's support for a more ambitious expedition: a fifteen- to eighteen-month tour of the western parts of the United States that he proposed Moses undertake in company with his cousin William Bartram "in order to make observations...upon the Natural productions of those regions." Their particular focus would be botany, Humphry Marshall emphasized, as "our western territories...abound with varieties of strange trees, shrubs, and plants, no doubt applicable to many valuable purposes in arts or manufactures" (). The expedition was still pending in 1788, when Moses Marshall told Lettsom that he "had a design highly favourable to discoveries in view,—a journey to the Mississippi, westward; but have not yet been at leisure to prosecute it." After returning from a 1,600-mile roundtrip excursion west to Pittsburgh and south to the Alatamaha River in Georgia, Marshall wrote to Sir Joseph Banks in London of his intention of making "a second, and yet more extensive route"(view text). Caspar Wistar immediately thought of Marshall when a group of gentlemen led by Thomas Jefferson were seeking an explorer in June 1792 to make an expedition up the Missouri river (view text). Marshall never seems to have made this long-deferred journey, which ultimately fell to Meriwether Lewis and William Clark.
Physical hardship and poor remuneration made the botanical business a difficult profession. In 1793 Marshall concluded a letter to one of his commercial clients in London with the acerbic remark, "Thus you may see to what fatigue, expense, and misfortune, we are subjected, who undertake to supply Europeans with curiosities; and judge how small our recompense" (). Following Marshall's appointment as Justice of the Peace of Chester County in April 1796, his engagement in the botanical business ceased. Thereafter, his uncle's botanic garden was "almost wholly neglected" and fell into ruin soon after Humphry Marshall's death in 1801.
- Marshall, Moses, June 27, 1784, letter from Bedford, Pa. to Humphry Marshall (Darlington 1849: 553) back up to history
- "These four days past, we have been amongst the Pine Mountains, where we have seen plenty of the Cucumber Trees, Rhododendrons, and Mountain Raspberry [Rubus odoratus, L.]: and yesterday, about Juniata, we found broad, willow-leaved Oak [Quercus imbricaria, Mx.?], and red-berried Elder.
- "In coming along, I have seen many strange plants; but may be chiefly varieties of what we have already. However, I shall gather what seed I can, of any such, or bring the plants."
- Marshall, Humphry, December 5, 1785, letter to Benjamin Franklin (Darlington 1849: 522–523) back up to history
- "I had it in contemplation to mention to thee for thy approbation, or sentiments thereon, a proposal that I had made, last winter, to my cousin, WM. BARTRAM, and nephew, Dr. MOSES MARSHALL, of taking a tour, mostly through the western parts of our United States, in order to make observations, &c, upon the Natural productions of those regions; with a variety of which, hitherto unnoticed, or but imperfectly described, we have reason to believe they abound; which, on consideration, they at that time seemed willing to undertake, and I conceive would be so still, provided they should meet with proper encouragement and support for such a journey; which they judge would be attended with considerable expense, for the transportation of their collections, &c, and for their subsistence during a period of fifteen or eighteen months, or more, which would at least be necessary for the completion of the numerous observations, and objects they would have to make remarks on, and collect. Should such proposals be properly encouraged, I apprehend they would engage to set out early in the spring, and throughout their journey make diligent search and strict observation upon everything within the province of a naturalist; but more especially upon Botany, for the exercise of which there appears, in such a journey, a most extensive field; for, from accounts of our western territories, they are said to abound with varieties of strange trees, shrubs, and plants, no doubt applicable to many valuable purposes in arts or manufactures, and to be replete with various species of earths, stones, salts, inflammable minerals, and metals (the many uses of obtaining a knowledge of which is sufficiently obvious); remarks, experiments, &c, upon every of which they propose making; as also to make collections, and preserve specimens, of everything that may enrich useful science, or amuse the curious naturalist; to the conducement of which, they would willingly receive and observe any reasonable instructions that might facilitate their discoveries, or direct their researches.
- "I have taken the freedom to mention these proposals to thee knowing that thou was always ready and willing to promote any useful knowledge and science, for the use of mankind; and if, on consideration of the premises, thou should approve thereof, thou may communicate them to the members of the Philosophical Society, or any other set of gentlemen, that would be willing or likely to encourage such an undertaking. Perhaps Congress, or some of the members, might promote their going out with the surveyors, when they lay out the several new states.
- "I have ordered my nephew, the Doctor, to present thee with one of my Catalogues of the Forest Trees of our Thirteen United States; which I hope thou'll accept of, for thy perusal."
- Marshall, Humphry, November 14, 1786, letter from West Bradford, Pa. to Sir Joseph Banks (Darlington 1849: 560–562) back up to history
- "I received thy favour, dated April the 5th, 1786, in which thou seems desirous of trying an experiment upon the curing the root of Ginseng; for which purpose thou desires that I would procure thee one or two hundred weight of the fresh root... which requisition I have endeavoured to comply with, but have not been able to procure for thee more than about one hundred weight of the fresh root, and that at a considerable expense; having to employ a young man, a nephew of mine [Moses Marshall], that lives with me, to travel about two hundred miles to the westward, through a dismal mountainous part of our country, as the Ginseng is either dug up for sale, or rooted up by the hogs so much, that it begins to grow scarce in the inhabited parts....
- "He was likewise obliged to hire a person, at a dollar a day, to assist him in digging said Ginseng, both of them being obliged to encamp in the mountains, strike up a fire and lie by it all night, in the morning take their hoes and knapsacks on their backs, and climb up the sides of the mountains, and dig till towards evening, and then bring what they had dug to their camp, and cook their morsel and eat it. It took him about twenty days, in going and coming home again, digging the roots, and packing up, &c., the expense of carriage being considerable. Therefore, it being procured and carefully put up according to thy direction, I hope that it may arrive safe; and if so, I expect thou'll be willing to pay a reasonable compensation, which would be, at least, an English crown a pound, I should apprehend. But, if thou thinks that too much, be pleased to pay what thou thinks would be a compensation, adequate to the trouble and cost the young doctor hath been at; and I hope, if thou, or any of the members of the Royal Society, should see cause to employ him, or me, in future, that we would endeavour to serve you as reasonable as any other persons; and as my nephew is well versed in the knowledge of Botany, and would gladly be employed in researches in that line, or to explore our western regions in search of minerals, fossils, or inflammables, and objects of History, &c., provided he could meet with proper encouragement, I, therefore, make free to mention something of the kind to thee, that if the Royal Society should have a mind to employ any person, on this side the water, for such purposes, he would be willing to serve them.
- "I have sent thee one of my pamphlets, entitled the American Grove, and expect thou'll present it to the Royal Society, in my name, if thou thinks it worth their notice and acceptance; as also one for thyself, which I hope will be accepted....
- "If any more should be wanted, perhaps it might be procured some small matter reasonabler than this sent, my nephew having found, in his route, where it grows pretty plenty."
- "I have an idea if thy nephew could spare the time to come to this country even for a short time he might find a great advantage in observing which plants are the most valuable & scarce here—am told that when the Scaret Azalea was first introduced here a single plant was sold for £40 to a nurseryman for propagation."
- Wistar, Caspar, October 21, 1787, letter to Humphry and Moses Marshall (Darlington 1849: 568–569)
- "With this I send a Treatise on the effects of Foxglove, which I mentioned to friend H. M. when he was last in town. Dr. M. will he pleased to find that he is in possession of a plant of such efficacy, and perhaps will cultivate a greater quantity of it. As the book is in great demand, I wish he would return it by the first opportunity that offers, after he has read it.
- "If you have any of the plant to spare, I will be much obliged to you for a few leaves of it, and also a few seeds, with the book, when it is returned."
- Marshall, Moses, May 7, 1788, letter from Bradford, Pa. to John Coakley Lettsom (Darlington 1849: 545–548) back up to history
- "In a corner of the box, are a few small plants, which I believe are yet undescribed, viz., a species of Sedum; a species of Portulaca, the root perennial, the stem short, thickly set with cylindrical succulent leaves standing somewhat erect; from the centre shoots forth a very slender, naked, reddish stem, four or five times the length of the leaves, branching at top, and supporting reddish flowers, which expand about noon, and continue open about three hours. Also a species of Veronica, and a small Evergreen from the mountains, the characters of which I have attempted drawing though from the dissection of but a single flower: ...[Linnaean description follows]
- "To this plant, should it prove to be a new genus, I had some time since designed the appellation of Lettsomia, with this provision, that it might not be unpleasing to thee, and that, in the interim, I should not be able to discover a plant more exalted, conspicuous, and worthy.
- "I have, indeed, had a design highly favourable to discoveries in view,—a journey to the Mississippi, westward; but have not yet been at leisure to prosecute it. I have, therefore, at present, but this humble offering to make.
- "The autumn will be more favourable for sending of plants, &c, at which time we shall endeavour to find something to furnish thy garden, or cabinet. In the mean time, I should wish thee to send LINNAEUS'S Genera and Supplementum Plantarum, the latest and best edition. Also, a surgeon's pouch, or case of pocket instruments.....
- "Residing with, and writing by direction of, my uncle, HUMPHRY MARSHALL."
- Muhlenberg, Rev. Henry, January 18, 1790, letter from Lancaster, Pa. to Humphry Marshall (Darlington 1849: 575–576) back up to history
- "As I know that your nephew has studied physic, I make bold to send him the late edition of LINNAEI Materia Medica, and hope the present will be not unacceptable. I have a great many botanical writings, and shall be happy if I can serve you or him in botanical researches, through a loan of them. Pray remember my best respects to him; and tell him how gladly I would embrace an opportunity of a correspondence, which certainly would be an advantage to our botanical studies....
- "I shall pass by your house, the latter end of May, on my way to Philadelphia; and then hope to see you, your nephew, and your garden."
- Marshall, Moses, October 30, 1790, letter to Sir Joseph Banks (Darlington 1849: 563–564) back up to history
- "Your order of April last, addressed to my uncle, was duly received; and in compliance therewith I send a box of plants....
- "In May last, I sat [sic] out upon a botanic tour, by way of Juniata to Pittsburg, thence southward, up the Monongahela, upon Green Briar River, over New River to Holston, Nolichucky, &c. Then crossing the high and great chain of mountains, came upon the head waters of Santee, in South Carolina; thence by Ninety-six to Augusta, and to Savannah town, and continuing southwest to the river Alatamaha, in Georgia. I here found the Franklinia or Gordonia sessilis, better called: i.e. floribus sessilibus.
- "I then returned to Charleston—making a route of about 1600 miles; and thence by water to Philadelphia—In this route, by reason of the unfavourable season of the year, I was unable to procure scarce anything but specimens. Of these, a few perhaps are new; but several are spoiled with dampness, &c. I designed forwarding the most curious; but through hurry left them at home; that is, thirty miles west of Philadelphia, from whence I now write. However, they shall be forwarded by another opportunity.
- "Notwithstanding the great fatigue, the danger, and expense in travelling, I have in contemplation a second, and yet more extensive route."
- Marshall, Moses, November 10, 1791, letter to Sir Joseph Banks (Darlington 1849: 565)
- "My attention has been diverted considerably, this summer, from botanical pursuits. I have, therefore, no specimens collected, having observed nothing new, except the small one inclosed.
- "The leaf you enclosed, desiring a specimen, is, I believe, a species of Ophrys, say hyemalis. I could not procure a flowering stem.
- "Astragalus Carolienisis I am not possessed of. The Podophyllum diphyllum [Jeffersonia] grows in great plenty, about two hundred and fifty miles to the westward, and not nigher, I believe....
- "If there are any particular objects you wish to be furnished with, or region of America you wish to be explored, I shall probably be at leisure one other summer.
- Muhlenberg, Rev. Henry, April 9, 1792, letter from Lancaster, Pa. to Moses Marshall (Darlington 1849: 576–577) back up to history
- "I beg leave to inform you, that the new edition of the Genera LINNAEI is safely arrived. The first volume arrived some time ago; the second very lately. The first is only bound in paper. I am happy to see that the editor, my friend D. SCHREBER, has done what I required from him. He has given your name to a hitherto undescribed plant, that belongs, to the Syngenesia, Polygamia oequalis, which he names Marshallia....
- "If you still incline to have them, pray let me know where to send them.
- "I intend... to be down your way this day a fortnight, on a journey to Philadelphia; and hope then to see you, and spend a few hours or more with you.
- "If you could spare me a plant of what your uncle calls Sedum verticillatum, I would be very glad to have it in my garden. It is a fine little plant."
- Wistar, Caspar, June 20, 1792, letter to Moses Marshall (Darlington 1849: 570) back up to history
- "By a conversation with thy uncle, I find that thee is already acquainted with the wishes of some gentlemen here, to have our continent explored in a western direction. My reason for writing, at present, is to inform thee of the present state of the business.
- "Mr. JEFFERSON and several other gentlemen are much interested, and think they can procure a subscription sufficient to insure one thousand guineas, as a compensation to any one who undertakes the journey, and can bring satisfactory proofs of having passed across to the South Sea.
- "They wish the journey to be prosecuted up the Missouri, as the easiest, and perhaps most interesting track. A Spanish gentleman who is now here, and lives near the mouth of the Missouri, says that a caravan of traders go off every year up the Missouri, and penetrate fifteen hundred miles up it, to the Mahaw indians, who are very friendly indeed. These traders go off from the mississippi about the first of August, so that any one who thinks of it this year, ought to lose no time.
- "If thee has any inclination, I think it would be very proper to come to town immediately, and converse with Mr. JEFFERSON, who seems principally interested."
- Marshall, Moses, December 11, 1793, letter to Grimwood, Hudson, and Barret (Darlington 1849: 580–582) back up to history
- "Yours of the 18th June, I duly received; and in compliance therewith, have herewith sent...one box plants, and one small box of seeds....
- "We... [during Yellow Fever outbreak] became careless in procuring some things, especially those at a distance, till too late; as the Juniperus and Rhododendron seeds. The Sarracenia purpurea, Helonias asphodeloides, and Cypripedium acaule, natives of New Jersey, at sixty miles distance, the route through Philadelphia, were not procured from the above cause; though these I still designed to get: yet, the day on which I had purposed setting out on that errand, there fell a snow eighteen inches in depth. Thus, you see, though the intention to serve you was good, yet it has been in part diverted and defeated, by intervening casualties.
- "The Magnolia auriculata cannot be had, I believe, without going to the place of its native growth; which is (at least, what I have seen,) in South Carolina, about two hundred miles from the sea-coast. I have but one plant; and BARTRAM two or three, which he does not incline to part with. There are some, that M. MICHAUX, a French botanist, procured, and sent from Charleston, a few years since. But he has since been in Canada, and I believe is now in Kentucky.
- "Of the Magnolia grandiflora, I have two fine plants, too large to send abroad. I am in nearly the same situation with respect to Stuartia and Fothergilla. There is none to be had nearer than Carolina; where also grows the Sarracenia flava.
- "With respect to new things, when I consider that a KALM and a CLAYTON have been here, I have little hopes of making discoveries: yet I find there are many little plants that escaped their view. In a circuitous route of about seven hundred miles, which I took this summer, I have observed several small herbaceous, and two shrubby plants, which I believe are new. One of the shrubs is, perhaps, a Spiraea: the other, the Oily Nut [Pyrularia, Mx., Hamiltonia oleifera, Muhl.], of which I formerly sent a specimen to Sir JOSEPH BANKS. It grows to the height of six or eight feet; the flowers are small, and make little appearance; but the fruit is perfectly oily....
- "As I have discovered this to grow at the distance of only two hundred and fifty miles, if those I now have should not shoot, in the spring, I intend setting out for a new supply. Thus you may see to what fatigue, expense, and misfortune, we are subjected, who undertake to supply Europeans with curiosities; and judge how small our recompense."
- Parke, Thomas, October 19, 1796, letter from Philadelphia to Humphry and Moses Marshall (Darlington 1849: 532)
- "I have received a letter from ROBERT BARCLAY, which contains the following paragraph:—
- "'Pray desire H. and M. Marshall to send me a box of plants for my friend T. KITT, of Norwich, who is well versed in plants, and will be pleased with a nice collection, mixed as usual with herbaceous; remembering to add several Kalmias, Azaleas, &c., and everything new or curious.'"
- Hamilton, William, November 23, 1796, letter from The Woodlands to Humphry Marshall (Darlington 1849: 578)
- "When you were last here it was so late, and you were of course so much hurried, as to prevent your deriving any satisfaction in viewing my exotics. I hope when you come next to Philadelphia, that you will allot one whole day, at least, for the Woodlands....
- "Your nephew [Moses Marshall] did me the favour of calling, the other day; but he, too, was in a hurry, and had little opportunity of satisfying his curiosity. I flatter myself, however, that during his short stay he saw enough to induce him to repeat his visit. The sooner this happens, the more agreeable it will be to me.
- "When I was at your house, a year ago, I observed several matters in the gardening way, different from any in my possession. Being desirous to make my collection as general as possible, I beg to know if you have, by layers, or any other mode, sufficiently increased any of the following kinds so as to be able, with convenience, to spare a plant of each of them, viz. ... two kinds of a genus supposed, by Dr. MARSHALL, to be between Uvularia and Convallaria [probably the Streptopus, of MICHAUX, which the MARSHALLS proposed to call Bartonia]."
- Hamilton, William, May 3, 1799, letter from The Woodlands to Humphry Marshall (Darlington 1849: 579–580) back up to history
- "I have not heard of Dr. MARSHALL'S having been in this neighbourhood since I was last at Bradford. From the pressing invitation I gave him, I am willing to hope that, in case of his coming to town, he will not forget to give me a call. I beg you will present him with my best respects, and request of him to give me a line of information, as to the Menziesia ferruginea, particularly of its vulgar name, if it has one, where it grows, if he knows the name of any person in its neighbourhood, who is acquainted with it, so, as to direct or show it to any one who may go to look after it.
- "I intend, next month, to go to Lancaster; and if convenient to me, when there, to spare my George, I have thoughts of sending him to Redstone, for the Menziesia, and Podophyllum diphiyllum. If Dr. MARSHALL knows of any curious and uncommon plants, growing in the neighbourhood with those I have mentioned, I will be obliged to him to give me any intelligence by which he may suppose they can be found: or, if he knows any person or persons at Redstone, or Fort Pitt, who are curious in plants, of whom any questions on the subject may be asked, he cannot do me a greater service than by giving me their names and place of abode."
- Mease, Dr. James, February 23, 1803, letter to Moses Marshall (quoted in Gutowski 1988: 153)
- "Dr. Barton has just published his Elements of Botany. It is an excellent work, and will do him credit. He says the oil-nut 'is a new Pentandrous genus of plants, allied to Nerium. It is a native of Pennsylvania; Virginia, and other parts of the U. States.' You shall not be deprived of the merit of the discovery of this genus: that is to say, provided you are desirous of having the merit attached to your name....I must notice it; in my work. Say at what time you discovered iti and where. If I were not so engaged every day in correcting a proof sheet, I would go to Pittsburgh, with my friend Rafinesque, and describe the plant, this summer."
- Anonymous, May 10, 1828, history of Humphry Marshall's Botanic Garden, ("Chester County Cabinet of Natural Science," 1828: 302–303)
- "After the decease of Mr. Humphrey [sic] Marshall, in the year 1801, we believe that no improvements were made in the garden, and since the death of Doctor Moses Marshall, in 1813, the Botany of the place seems to have been entirely neglected....
- "In 1785, he published the Arbustum Americanum, or catalogue of American Forest Trees and Shrubs, in which he was assisted by his nephew, the late Doctor Moses Marshall, who was a botanist of considerable merit, and, at the request of his uncle, had travelled through many of the States, in search of American plants."
- Darlington, William, 1843, on the impact of Moses Marshall and the Marshallton Botanic Garden (1843: 8–9)
- "[William] BALDWIN had become intimate with the late Dr. MOSES MARSHALL,—nephew and heir of HUMPHRY MARSHALL, the well-known author of the Arbustum Americanum, and founder of the Botanic Garden at Marshallton. This gentleman was a respectable Botanist, and had materially assisted his uncle,—both in the establishment of his Garden, and in the preparation of his work on American Forest Trees and Shrubs. In the society of Dr. MARSHALL, BALDWIN had his taste for the study of the vegetable creation first awakened; and the means of gratifying it were amply afforded by the rich collection of indigenous plants, then growing in the Botanic Garden. This circumstance undoubtedly gave a decided bias to his future pursuits; and illustrates well the happy influence of such institutions, and opportunities, in developing the latent powers and aptitudes of ingenuous Youth."
- "For several years prior to the establishment of the Marshallton Garden, Humphry had been much engaged in collecting native plants and seeds, and shipping them to Europe; but after that event, being aided by his nephew, Dr. Moses Marshall, he greatly extended his operations, and directed his attention with enhanced zeal and energy to the business of exploring, and making known abroad, the vegetable treasures of these United States. The present generation of botanists have but an imperfect idea of the services rendered to the science, by the skill and laborious industry of those faithful pioneers; but the letters here given, will show that they contributed largely to the knowledge of American plants.
- "After practising Medicine a short time, he [Moses Marshall] seems to have become an inmate in the family of his uncle HUMPHRY, devoting his time and services, exclusively, as an aid to his uncle, in the business of collecting and shipping plants and seeds to Europe. He made several long exploring journeys, in that pursuit, through the wilds of the West and Southwest. He was a good practical botanist, well acquainted with most of our indigenous plants, and rendered valuable assistance to his uncle, in preparing the Arbustum Americanum.... The editor had the happiness to know him well, and passed many pleasant, instructive hours with him, investigating the plants in the Marshallton Botanic Garden. Dr. MARSHALL discontinued the business of sending plants and seeds to Europe, soon after his uncle's death, and the garden, in consequence, has ever since been almost wholly neglected."
- John William Harshberger, The Botanists of Philadelphia and Their Work (Press of T. C. Davis & Son, 1899), 96–97, 99–101, view on Zotero.
- In a letter of May 7, 1788 to John Coakley Lettsom, Marshall described himself as "Residing with, and writing by direction of, my uncle." See William Darlington, Memorials of John Bartram and Humphry Marshall: With Notices of Their Botanical Contemporaries (Philadelphia: Lindsay & Blakiston, 1849), 545–548, view on Zotero.
- For Marshall's letter-books in the Manuscripts Division, William L. Clements Library, University of Michigan, view website.
- Anonymous, "Chester County Cabinet of Natural Science," The Register of Pennsylvania 1 (May 10, 1828): 302, view on Zotero; William Baldwin, Reliquiae Baldwinianae: Selections from the Correspondence of the Late William Baldwin with Occasional Notes, and a Short Biographical Memoir, ed. William Darlington (Philadelphia: Kimber and Sharpless, 1843), 8, view on Zotero; Darlington 1849, 546, view on Zotero.
- Humphry Marshall reportedly began the Arbustum in 1780. Samuel Vaughan presented the completed manuscript before the Society for Promoting Agriculture in April 1785. See Darlington 1849, 489, 555, view on Zotero; Harshberger 1899, 101, view on Zotero.
- List of plants required for Kew Garden, compiled by William Aiton and forwarded by Sir Joseph Banks to Moses Marshall, March 3, 1791, with note written in the hand of Banks; Papers of Sir Joseph Banks, CY3681/292 (Series 20.43), State Library, New South Wales, accessed 11/27/2015.
- Johann Jakob Reichard, May 30, 1791, letter from Belvedere near Weimar, Germany, to Moses Marshall, Scrapbook 5 [Manuscript 77046], Item 1482, Buffington–Marshall papers, MS.Coll.168, Chester County Historical Society.
- James M. Walton, August 22, 1791, to letter from Charleston, South Carolina, to Moses Marshall, Scrapbook 5 [Manuscript 77046], Item 1483, Buffington–Marshall papers, MS.Coll.168, Chester County Historical Society.
- Darlington 1849, 548–549, view on Zotero.
- R. B. Channell, "A Revisional Study of the Genus Marshallia (Compositae)," Contributions from the Gray Herbarium of Harvard University 181 (1957): 41–130, view on Zotero; Harshberger 1899, 104, view on Zotero.
- Darlington 1849, 547, view on Zotero.
- Harshberger 1899, 105–107, view on Zotero.
- Darlington 1849, 545–546, view on Zotero.
- Darlington 1849, view on Zotero.
- John W. Harshberger, "Additional Letters of Humphry Marshall, Botanist and Nurseryman," Pennsylvania Magazine of History and Biography 53 (1929), view on Zotero
- CCHS, Darlington Manuscript, 861; quoted in Robert R. Gutowski, "Humphry Marshall’s Botanic Garden: Living Collections 1773–1813" (unpublished Master of Science in Public Horticulture Administration, University of Delaware, 1988), view on Zotero.
- Anonymous, May 10, 1828, view on Zotero.
- Darlington 1843, view on Zotero.