Asa Gray by John Adams Whipple, 1864.
November 18, 1810|
Sauquoit, New York
|Died||January 30, 1888
|Nationality||United States of America|
He was instrumental in unifying the taxonomic knowledge of the plants of North America. Of Gray's many works on botany, the most popular was his Manual of the Botany of the Northern United States, from New England to Wisconsin and South to Ohio and Pennsylvania Inclusive. This book, known simply as Gray's Manual, has gone through a number of editions with botanical illustrations by Isaac Sprague, and remains a standard in the field.
Early life and education
Gray was born in Sauquoit, New York in November 18, 1810 to Moses Gray (b. February 26. 1786),[a] then a tanner, and Roxanna Howard Gray (b. March 15, 1789) Gray was born in the back of his father's tannery and was the eldest of their eight children. Gray's Scotch-Irish Presbyterian ancestors moved to New York from Massachusetts and Vermont after Shays' Rebellion. His paternal great-grandfather arrived in Boston from Northern Ireland in 1718. His parents married July 30, 1809. Gray was an avid reader even in his youth. Tanneries needed a lot of wood to burn and the lumber supply in the area had been shrinking. So Gray's father used his profits to buy farms in the area and about 1823 sold the tannery and became a farmer.
Gray completed Clinton Grammar School from about 1823 to 1825. During this time he read many books from the nearby library at Hamilton College. Then in 1825 he enrolled at Fairfield Academy, switching to its Fairfield Medical College, also known as the Medical College of the Western District of Fairfield, in autumn 1826.[b] It was during this time that Gray began to mount botanical specimens. On a trip to New York City, he attempted to meet with John Torrey to get assistance in identifying specimens, but Torrey was not home, so Gray left the specimens at Torrey's house. Torrey was so impressed with Gray's specimens that began a correspondence with Gray. Gray graduated and became an M.D. in February 1831, even though he was not yet 21 years of age, which was a requirement at the time. Gray did open a medical office in Bridgewater, New York, though he never truly practiced medicine as he enjoyed botany more. Bridgewater is where he had served an apprenticeship with Doctor John Foote Trowbridge while he was in medical school. It was around this time that he began making exploring expeditions in New York and New Jersey. By autumn 1831 he had essentially given up his medical practice to devote more time to botany.
In 1832 he began teaching Chemistry, Mineralogy, and Botany at Bartlett's High School, in Utica, New York and also at Fairfieled Medical School. This was because the school's instructors had died in mid-term. Gray agreed to teach for one year, which included a break from August-December 1832, causing him to cancel his plans for an expedition to Mexico, which at the time included what is now the southwestern United States. Gray first met Torrey in person in September 1832 and they went on an expedition to New Jersey. After finishing teaching in Utica on August 1, 1833, Gray became an assistant to John Torrey of the College of Physicians and Surgeons in New York City. By this time Gray was corresponding and trading specimens with botanists not just in America, but Asia, Europe, and the Pacific Islands as well. Gray had a temporary teaching position in 1834 at Hamilton College. Due to funding shortages as Torrey's assistant, in 1835 Gray left his job as Torrey's assistant and in February or March 1836 became Curator and Librarian at the Lyceum of Natural History in New York, which is now called the New York Academy of Sciences. He even had an apartment in their new building in Manhattan. Torrey's attempt to get Gray a job at Princeton University was unsuccessful, as did other attempts to find a position in science. Despite this departure, Torrey and Gray became lifelong friends and colleagues. It was Torrey's wife, Eliza Torrey, who had a profound impact upon Gray in that his manners, tastes, habits, and religious life manners.
In October 1836 Gray was selected to be one of the botanists on the United States Exploring Expedition, also known as the "Wilkes Expedition", which was supposed to last three years. Gray began getting paid well for preparations and planning for this expedition; even to the point of loading supplies onto a ship in New York harbor. However, the expedition was fraught with politics, bickering, turmoil, inefficiency, and delays. Referring to the Secretary of the Navy, Mahlon Dickerson, Gray wrote of "abominable management & stupidity". Despite this, Gray resigned from the Lyceum in April 1837 to devote full-time to the expeditions preparations. By 1838 the expedition was in utter turmoil. The new state of Michigan was starting its university and Gray applied for a professorship in early 1838. He resigned from the Wilkes Expedition on July 10, 1838.
On July 17, 1838, Gray became the very first permanent paid professor at the newly founded University of Michigan, though he never taught classes there. His position was also the first one devoted solely to botany at any educational institution in America. Appointed the Professor of Botany and Zoology, Gray was dispatched to Europe by the regents of the university for the purpose of purchasing a suitable array of books to form the university's library and equipment such as microscopes to aid research. Botanist Charles F. Jenkins states that the main purpose of this trip was to examine American flora in Europe's herbariums. In 1839 the regents purchased a complete copy of Audubon's The Birds of America for the then extraordinary sum of $970. He departed on the ship packet ship Philadelphia on November 9, 1838, sailing through The Narrows, nine days before his 28th birthday. Gray and the regents were both involved in stocking the university library. Gray's first stop was in Glasgow, visiting William Hooker, who aided and financially supported many botanists, including Gray. On January 16, 1839, he arrived in London and stayed until March 14, 1839. He then spent a lot of time in Paris, where he collaborated with Joseph Decaisne at the Jardin des Plantes. In mid-April 1939, he left Paris for Italy by was of southern France, then visiting Genoa, Rome, Florence, Venice, Blogna, Padua, and Trieste. After Italy, Gray went to Vienna, Austria. While in Vienna, he spent 12 days studying specimen collections and gardens with Stephan Endlicher, who also introduced him to other local botanists. In 1840, Endlicher became director of the Botanical Garden of the University of Vienna. Departing Austria, he went to Munich, Zurich, and Geneva, where he met the prominent botanist Augustin Pyramus de Candolle, who died in 1841. Gray continued extensive collaboration with de Candolle's sons. Gray returned to Germany, going to Freiburg, Tübingen, Dresden, Halle, and then Berlin, where he stayed a month. While in Berlin, he spent most of his time in Schöneberg, which is where the region's Botanical Gardens were then located. Gray then returned to London by way of Hamburg. Gray admitted he just managed some of the book purchasing and that he delegated the actual buying of books to George Palmer Putnam, who was then living in London. Gray spent a year in Europe, returning to America from Portsmouth, England aboard the sailing ship Toronto on October 1, 1839. Gary arrived back in New York on November 4, 1839. Gray, together with his agents, eventually purchased about 3,700 books for the University of Michigan library. The regents at the University of Michigan were so impressed by Gray's work in Europe, including his spending about $1,500 of his own money on specimen collections, they granted him another year's salary that covered him until the summer of 1841. However, finances at the university were so bad that they asked him to resign in April 1840.
While he was in Paris at the Jardin des Plantes, Gray saw an unnamed specimen and named it Shortia galacifolia. He spent considerable time and effort looking for a specimen in the wild for the next 38 years. The first such expedition was in late June to late July 1841 to an area near Jefferson, Ashe County, North Carolina. Further expeditions by Gray searching for this species were also unsuccessful. In May 1877 a North Carolina herb collector found a specimen but did not know what it was. Eighteen months later the collector sent it to Joseph Whipple Congdon, who contacted Gray, telling Gray that he felt he had found Shortia. Gray was ecstatic to confirm this when he saw the specimen in October 1878. In spring 1879 Gray led an expedition, in which the collector helped, to the spot where S. galacifolia had been found. Gray never saw this species in the wild in bloom.
Both Gray and Torrey were elected to the American Academy of Arts and Sciences in December 1841. Gray never returned to teach a course at Michigan. In 1833, Dr. Joshua Fisher, resident of Beverly, Massachusetts and a Harvard University alumnus, bequeathed $20,000 to Harvard to endow a chair in natural history. The university allowed the proceeds to accumulate until it could fund a full year's salary for a professor. Because of this and a few problems in finding a suitable professor, this chair was not filled until 1842, when Gray was formally offered the professorship on March 26, 1842. The offer was $1000/year salary, teaching duties limited to only botany, and being superintendent of Harvard's botanic garden. While $1000 was low for the time, the teaching limitation, rare for the time, allowed him plenty of time to do research, plus he got to work in the botanic garden. After an exchange of letters, Gray accepted this appointment as Fisher Professor of natural history at Harvard. The formal appointment was made April 30, 1842. Gray arrived at Harvard on July 22, 1842 and began his duties in September. However, he did not have to teach classes in the Fall of 1842, his Spring 1843 classes were the first one he taught in nine years. Early in his years at Harvard Gray had to borrow money from his father. Soon he was able to repay his father and help his family because he supplemented his income by giving lectures outside of Harvard, including at the Lowell Institute. Gray was considered a weak lecturer, but because of his expert knowledge, he was highly regarded by his peers. His skills were better suited to teaching advanced rather than introductory classes. He also gained renown for his textbooks and high quality illustrations. Gray moved into the Asa Gray House, which was in the Botanic Garden, in the summer of 1844. It had been built in 1810 for William Dandridge Peck and later occupied by Thomas Nuttall. As the demands of teaching, collecting, selling specimens, taking care of the herbarium, and writing books increased and he himself was not a good illustrator, Gary found it necessary to hire a botanical illustrator--Isaac Sprague, who illustrated much of Gray's works for decades to come.
By June 1848 many of the specimens from the Wilkes Expedition had been damaged or lost. Much of it was still not classified or published as the mismanagement and bungling that plagued the expedition before it ever departed continued. While on a trip to Washington D.C. that month with his new bride, with his wife, Gray was hired to study the botanical specimens for five years. This included a year in Europe, with his wife, using the facilities at the herbariums in Europe.Mr. and Mrs. Gray departed for England on June 11, 1850. They spent the summer traveling to Belgium, Switzerland, Germany, and the Netherlands. Gray then set down to expedition's plant sheets at the estate of botanist George Bentham, whom he had met 11 years earlier, and then with William Henry Harvey in Ireland. Gray returned to England and settled down into a routine at the Royal Botanic Gardens, Kew. The couple was back in America on September 4, 1851. In the meantime a dispute had arisen between Wilkes and the team of Torrey and Gray about the format of the books resulting from the expedition. Gray almost hired his father-in-law to break the contract. This dispute largely centered on the use of Latin and English. Wilkes wanted a literal Latin to English translation while Torrey and Gray wanted a looser one they felt technical English terms were equally incomprehensible to the public. Much of the work was stymied or burned in fires.
During late summer of 1855, Gray made his third trip to Europe. This was an emergency trip to bring home his ill brother-in-law from Paris. Gray spent only three weeks in London and Paris and on the way back he read the newly published Géographie botanique raisonnée by Alphonse Pyramus de Candolle, son of the elder Candolle. This was a ground-breaking book that for the first time brought together the large mass of data being collected by the expeditions of the time. The natural sciences had become highly specialized yet this book synthesized them to explain living organisms within their environment and why plants were distributed the way they were, all upon a geologic scale. Gray instantly saw that this brought taxonomic botany into focus.
Despite Gray constantly seeking collectors and people to help him with the Harvard herbarium, in the first 15 years he was at Harvard, no graduate entered botany as a career. This changed in 1858 with the arrival of Daniel Cady Eaton, who had graduated from Yale University in 1857 and came to Harvard to study with Gray. Eaton would return to Yale to be a botany professor and oversee its herbarium, just like Gray did at Harvard. Daniel Eaton was the grandson of Amos Eaton, whose textbooks Gray had studied from during his college days. Amos Eaton influence the teaching style of Gray, wherein both required practical work of their students. He retained the Fisher post until 1873 while lived in the Asa Gray House.
In 1864 Gray donated 200,000 plant specimens and 2,200 books to Harvard with the condition the herbarium and garden be built. This effectively created the botany department at Harvard and the Gray Herbarium was named after him. He was President of the American Association for the Advancement of Science in 1872 and of the American Academy of Arts and Sciences 1863-1873. In 1859, he was elected a foreign member of the Royal Swedish Academy of Sciences. Gray was also Smithsonian Institution regent from 1874–1888 and a foreign member of the Royal Society of London in 1873.
The Elements of Botany (1836), an introductory textbook, was the first of Gray's many works. In this book Gray espoused the idea that botany was useful not only to medicine, but also to farmers. Gray and Torrey published the Flora of North America together in 1838. By the mid-1850s the demands of teaching, research, gardening, collecting, and corresponding had become so great and he had become so influential that Gray wrote two high school level texts in the late 1850s: First Lessons in Botany and Vegetable Physiology (1857) and How Plants Grow: A Simple Introduction to Structural Botany (1858). The publishers had to pressure Gray to make these two books non-technical enough so that high school students and non-scientists could understand them. As with most scientists in American academic institutions, Gray found it difficult to concentrate purely on research.
Gray met physician and botanist George Engelmann in the early 1840s and they remained friends and colleagues until Engelmann died in 1884. Torrey was an early American supporter of the "natural system of classification", which relies upon geography and a plant's entire structure and as his assistant, Gray was a proponent of this system too. This contrasts with Linnaeus' artificial classification, which was designed for ease of use and focused on readily observed aspects of a plant, particularly the differences in the flowers. Amos Eaton was also a proponent of the artificial system. Gray was so impressed with Wilhelm Nikolaus Suksdorf, a largely self-taught immigrant from Germany that specialized in flora of the Pacific Northwest, that he had Suksdorf come to Harvard to be his assistant and named the genus Suksdorfia after him.
Gray was a leading opponent of the Scientific Lazzaroni, a group of mostly physical scientists who wanted to American academia to mimic the autocratic academic structures of European universities. This is one of the areas where Gray and his friend and colleague, Louis Agassiz were in disagreement; Agassiz was a member of this group. Agassiz had came to lecture at the Lowell Institute in 1846 and got hired by Harvard in 1847. Gray befriended him the way he had been befriended during his trip to Europe. Another area where they strongly disagreed was on the theories of Charles Darwin. Agassiz was adamantly opposed to them whereas Gray was a staunch supporter.
Gray abhorred slavery. In his view science proved the unity of all man because all human races can interbreed and produce fertile offspring; ie, all members of a species are connected genetically. He also Christianity taught the unity of man. However, he was not an abolitionist, feeling it was more important to preserve the Union; yet he also felt if the South persevered in the conflict, every slave should be set free. This was another area where Gray and Agassiz disagreed Agassiz felt each race had different origins. Agassiz came to lecture at the Lowell Institute in 1846 and got hired by Harvard in 1847. Gray befriended him the way he had been befriended during his trip to Europe.
Gray received the following advanced degrees: honorary degree of Master of Arts (1844) and Doctor of Laws (1875) from Harvard, Doctor of Laws from Hamilton College (1860), McGill University (1884), and from the University of Michigan (1887).
The "Asa Gray disjunction"
Gray worked extensively on a phenomenon that is now called the "Asa Gray disjunction", namely the surprising morphological similarities between many eastern Asian and eastern North American plants. In fact, Gray felt the flora of eastern North America is more similar to the flora of Japan than it is to the flora of western North America, but more recent studies have shown this is not so. While Gray was not the first botanist to notice this (it was first noticed in the early 18th century), beginning in the early 1840s he brought scientific focus to the issue. He was the first scientist in the world to possess the requisite knowledge set to do so as he had intimate knowledge of the northeast and southeast United States as well as eastern Asia--due to several contacts he had there. The phenomenon involves about 65 genera and is not limited to plants, but also includes fungi, arachnids, millipedes, insects, and freshwater fishes. It was believed that each pair of species might be international sister species, but it is now known that this is not generally the case; the species involved are less closely related to one another. There are three possible causes for the observed morphological similarity, which likely developed at different times and via different pathways; the species pairs are: 1) the products of similar environmental conditions, 2) relicts of species that were widely distributed in the early Tertiary but diversified since then, probably during the Miocene, 3) not as morphologically similar as was previously believed. Gray's work in this area gave significant support to Darwin's theory of evolution.
Research regarding the American West
Prior to 1840, besides what he had discovered during his trip to Europe, Gray's knowledge of the flora of the American West was limited to what he could learn from Edwin James, who had been on the expedition to the West of Major Stephen Harriman Long, and Thomas Nuttall, who had been on an expedition to the Pacific coast with Nathaniel Jarvis Wyeth. In the latter half of 1840, Gray met the German-American botanist and physician George Engelmann in New York City. Engelmann had a medical practice in Saint Louis. Engelmann took frequent trips to explore the American west and northern Mexico. The two remained close friends and botanical collaborators until Engelmann died in 1884. Engelmann would send specimens to Gray, who would classify them and act as a sales agent. Their collaborations greatly enhanced botanical knowledge of those areas. Another German-American botanist, Ferdinand Lindheimer collaborated with both Engelmann and Gray, focusing on collecting plants in Texas, hoping to find specimens with "no Latin names". Lowell helped fund these efforts. Another long term and productive collaboration was with Charles Wright, who collected in Texas and New Mexico on two separate expeditions in 1849 and 1851-1852. These trips resulted in publication of the two-volume Plantae Wrightianae in 1852-1853.
Gray traveled to the American west on two separate occasions, the first in 1872 and then again with Joseph Dalton Hooker, son of William Hooker, in 1877. Both times his goal was botanical research; avidly collecting plant specimens to bring back with him to Harvard. On his second trip through the American west, he and Hooker reportedly collected over 1000 specimens. They were accompanied for a time by Ferdinand Vandeveer Hayden, then in charge of the U.S. Geological and Geophysical Survey of the Territories. Gray and Hooker's research was reported in their joint 1880 publication, "The Vegetation of the Rocky Mountain Region and a Comparison with that of Other Parts of the World," which appeared in volume six of Hayden's Bulletin of the United States Geological and Geophysical Survey of the Territories.
On both trips he climbed Grays Peak, one of Colorado's many fourteeners. This mountain was named after Gray by the botanist and explorer of the Rocky Mountains Charles Christopher Parry. A nearby peak, Torreys Peak, was named after his mentor and friend John Torrey.
In 1880 David P. Penhallow was accepted by Gray as a research assistant. Penhallow aided in Gray's work regarding the distribution of northern hemisphere plants, and in 1882 Gray recommended Penhallow as a lecturer to Sr John Dawson of McGill University in Montreal, Canada.
Relationship with Darwin
Gray and Joseph Dalton Hooker went to visit Richard Owen at London's Hunterian Museum in January 1839. Gray met Charles Darwin during lunch that day at Kew Gardens, apparently introduced by Joseph Dalton Hooker. Darwin and Gray first corresponded in April 1855 when Darwin wrote Gray. Darwin found a kindred spirit in Gray as they both had an empirical approach to science. From 1855-1881 they exchanged about 300 letters. Darwin then wrote to Gray requesting information about the distribution of various species of American flowers, which Gray provided, and which was helpful in providing information for the development of Darwin's theory. This was the beginning of an extensive lifelong correspondence.
Gray, Darwin, and Hooker became lifelong friends and colleagues, and Gray and Hooker conducted research on Darwin’s behalf in 1877 on their Rocky Mountain expedition. After Hooker returned to England and reported to Darwin on their adventure, Darwin wrote back to Gray: “I have just... heard prodigies of your strength & activity. That you run up a mountain like a cat!”
By the early 1850s Gray had clearly defined his concept that the species is the basic unit of taxonomy. This was partly the result of the 1831-1836 voyage of the HMS Beagle, aboard which Darwin was the naturalist, during which Darwin discovered the differentiation of species among the various Galápagos Islands. Gray felt that like begat like and that if an individual was too different from its parents it would not be able to pass on its genes, hence the genetic barrier. Consequently, Gray was opposed to the idea of transmutation of species. Local geography could produce variances, like in the Galápagos and Hawaii, which Gray did get to study in depth like he wanted, but unlike species members cannot breed and reproduce. Gray was insistent that a genetic connection must exist between all members of a species. This concept was critical to Darwin's theories.
When Darwin received Alfred Russel Wallace's paper which described natural selection, Hooker and Charles Lyell arranged for a joint reading of papers by Darwin and Wallace to the Linnean Society. Since Darwin had nothing prepared, the reading included excerpts from his 1844 Essay and from a letter he had sent to Asa Gray in July 1857, outlining his theory on the origin of species. By that time Darwin was into writing the book. The correspondence with Gray was thus a key piece of evidence in establishing Darwin's intellectual priority with respect to the theory of evolution by natural selection. Neither Darwin nor Wallace attended the meeting. The papers were published by the society as On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection. By summer 1859 it was obvious to Gray and others working with Darwin that On the Origin of Species would be a ground breaking book.
Darwin published On the Origin of Species on November 24, 1859, six days after Gray's 49th birthday. The first printing was 1250 copies, with some having been sent to America via ship and one of those was for Gray. Gray's copy arrived just before Christmas and he read it between Christmas and New Year's. Since there was no international copyright law at the time, Gray also worked to protect the book from publishing piracy. Per American law at the time, a copyright could only be secured by an American edition being published by an American citizen and royalties were not required to be be paid to the author. Gray arranged the first American edition of On the Origin of Species and was able to negotiate royalties on Darwin's behalf. Gray took a 5% royalty from the publisher and Darwin was grateful for Gray's efforts that he offered Gray some of his royalties. Darwin held Gray in high esteem: he dedicated his book Forms of Flowers (1877) to Gray and he wrote in 1881 "there is hardly any one in the world whose approbation I value more highly than I do yours". Seeing the "unity we perceive in nature", Gray strongly objected to the idea of transmutation of species but not special creation. Perceiving law in the universe, he saw all species "that they not only had a Creatorm but have a Governor". Gray, considered by Darwin to be his friend and "best advocate", also attempted to convince Darwin in these letters that design was inherent in all forms of life, and to return to his faith. Gray saw nature as filled with "unmistakable and irresistible indications of design" and argued that "God himself is the very last, irreducible causal factor and, hence, the source of all evolutionary change." Darwin agreed that his theories were "not at all necessarily atheistical" but was unable to share Gray's belief. "I feel most deeply that the whole subject is too profound for the human intellect. A dog might as well speculate on the mind of Newton," he wrote.
Notwithstanding, though Gray was a Christian, he was a staunch supporter of Darwin in America, and collected together a number of his own writings to produce an influential book, Darwiniana (1876). These essays argued for a conciliation between Darwinian evolution and the tenets of theism, at a time when many on both sides perceived the two as mutually exclusive. Gray denied that investigation of physical causes stood opposed to the theological view and the study of the harmonies between mind and Nature, and thought it "most presumable that an intellectual conception realized in Nature would be realized through natural agencies".
In 1868 Gray had a year's leave of absence and visited Darwin in England – the first time they had met since they started their correspondence. Darwin had Gray in mind when he wrote that "It seems to me absurd to doubt that a man may be an ardent theist & an evolutionist."
Gray became engaged to Jane Lathrop[c] Loring of Boston in May 1847. Two of Gray's younger brothers, George and Joseph, were students at Harvard in the late 1840s and lived with Gray. During his junior year, George caught typhoid fever in late 1847 and died on January 9, 1848 in the Loring house in Boston. This is part of the reason Gray's marriage was delayed from Fall 1847 to Spring 1848. Gray and Jane Loring married on May 4, 1848. Her parents were Charles Greely Loring, a member of the Harvard Corporation and a lawyer, and Anna Pierce (Brace) Loring. Her family was Unitarian, like most faculty and staff of Harvard at the time. Both of them kept to their separate religious denominations yet seem to have had no difficulties over it. They had no children. Anna Gray accompanied her husband on most of his expeditions. Gray was a devout Presbyterian and was a member of First Church in Cambridge, a Congregational church, where he served as a Deacon. He was also an ardent empiricist in the tradition of John Locke and John Stuart Mill. When the congregation moved into its present building in 1872, at 11 Garden Street, Gray planted two yellowwood trees in front of the church. They stood until October 2014.
On November 28, 1887, as he was writing Grape Vines of North America, which is in the order Vitaceae, Gray became paralyzed and lingered for nine weeks. He died on January 30, 1888 and was buried at Mount Auburn Cemetery. The cemetery's Asa Gray Garden, with a central fountain and numerous unusual tree varieties, is named in his honor.
In 2011, the US Postal Service released an Asa Gray first-class postage stamp, as part of its American Scientists collection, along with Melvin Calvin, Maria Goeppert-Mayer, and Severo Ochoa. This was the third volume of this series. It features Shortia galacifolia, a flowering plant that fascinated Gray.
On Gray's 75th birthday, botanists led by editors of the Botanical Gazette presented Gray with a silver vase with the inscription "1810, November eighteenth, 1885. Asa Gray, in token of the universal esteem of American Botanists." An accompanying silver salver had the inscription "Bearing the greetings of one hundred and eighty botanists of North America to Asa Gray on his 75th birthday, Nov. 18, 1885."
- Gray's father's name was Moses Gray, whose full name may or may not have been Moses Wiley Gray. Moses Wiley Gray was the younger Moses' father, Asa Gray's grandfather. Asa Gray's father's name is also often reported as Moses Wiley Gray.
- This is sometimes mis-reported as 1829, but Gray himself wrote that it was 1826.
- Sometimes misspelled as Lothrop.
- Works by Asa Gray at Project Gutenberg
- Gray, Asa (1837). A Natural System of Botany. American. doi:10.5962/bhl.title.708.
- Gray, Asa; Torrey, John (1838–1843). A Flora of North America. I & II. New York: Wiley & Putnam. doi:10.5962/bhl.title.9466.
- Gray, Asa; Sullivant, William Starling (1848). A Manual of the Botany of the Northern United States. Boston: James Munroe and Company. doi:10.5962/bhl.title.10392.
- Gray, Asa; Wright, Charles (1852–1853). Plantae Wrightianae Texano - Neo-Mexicanae 1&2. Washington, D. C.: Smithsonian Institution.
- Gray, Asa (1857). First Lessons in Botany and Vegetable Physiology. New York: Ivison and Phinney.
- Gray, Asa (1858). How Plants Grow: A Simple Introduction to Structural Botany. New York: American Book Company.
- Gray, Asa (1862). Introduction to Structural and Systematic Botany and Vegetable Physiology. New York: Phinney & Company. doi:10.5962/bhl.title.3964.
- Gray, Asa (1876). Darwiniana: Essays and Reviews Pertaining to Darwinism. New York: Appleton & Company. doi:10.5962/bhl.title.19483. LCCN 04005631. OCLC 774014.
- Gray, Asa (1878–1897). Synoptical Flora of North America. New York: American Book Company. doi:10.5962/bhl.title.10847.
- Gray, Asa (1879). Gray's Botanical Text-book. I & II. New York: American Book Company. doi:10.5962/bhl.title.1355.
- Gray, Asa; Hooker, Joseph Dalton (1880). "The Vegetation of the Rocky Mountain Region, and A Comparison With That of Other Parts of the World". Bulletin of the United States Geological and Geographical Survey of the Territories (Washington, DC: United States Government Printing Office) VI (1): 1–77.
- Gray, Asa (1887). Gray's School and Field Book of Botany. New York: American Book Company. doi:10.5962/bhl.title.55588.
- Gray, Asa (1888). Synoptical Flora of North America: The Gamopetalae. I, pt. II, and II, pt. I (2 ed.). Washington, DC: Smithsonian Institution. doi:10.5962/bhl.title.1520.
- Biographies of Scientists and Explorers 2015.
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- Farlow 1889, p. 163.
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- Farlow 1889, p. 164.
- Gray 1894, pp. 12-14.
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- Deane 1888, pp. 59-72.
- Gray 1894, pp. 14-18.
- Encyclopaedia Britannica 2013.
- Dupree 1988, pp. 15, 18-20, 22.
- Dupree 1988, pp. 23-24.
- University of Michigan 2015.
- Dupree 1988, pp. 30-32.
- Dupree 1988, pp. 33-36.
- Dupree 1988, pp. 35, 50.
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- Dupree 1988, pp. 41-43, 56-57.
- Farlow 1889, pp. 164-165.
- Dupree 1988, pp. 43-44, 47-50.
- Dupree 1988, p. 38.
- Torrey 1988, pp. 221-228.
- Dupree 1988, p. 62.
- Dupree 1988, pp. 59-65, 67-68.
- Pitcher 1856, p. 79.
- Dupree 1988, pp. 67-68.
- Dupree 1988, pp. 68-74.
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- Donnelly 1958, p. 1359.
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- Dupree 1988, p. 88.
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- Dupree 1988, pp. 91-92.
- Dupree 1988, pp. 93-94.
- Jenkins 1942, pp. 16-18.
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- Jenkins 1942, pp. 13-28.
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- Dupree 1988, pp. 106-108.
- Dupree 1988, pp. 110-115.
- Dupree 1988, pp. 117, 122.
- Dupree 1988, pp. 126-127.
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- Dupree 1988, pp. 166-167.
- Dupree 1988, pp. 185-190, 194.
- Dupree 1988, p. 191.
- Dupree 1988, pp. 193-195.
- Dupree 1988, pp. 235-236.
- Dupree 1988, pp. 197-198.
- Dupree 1988, pp. 15, 28-29, 200.
- National Park Service 2015.
- Darwin Correspondence Project 2015.
- Gray Herbarium 2015.
- Litchfield Historical Society 2014.
- Dupree 1988, pp. 51-53.
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- Dupree 1988, pp. 202-204, 212-213.
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- Dupree 1988, pp. 97-98.
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