H.W. Rudolf Marloth, analytical chemist and perhaps the greatest of all South African botanists, completed his schooling at the Real Gymnasium, Luebben, in 1873 and for the next three years trained as a pharmacist in the same town. He subsequently worked for various pharmacies in Germany and Switzerland. At this time he already had a strong interest in botany and had collected and preserved many plants. In April 1880 he enrolled at the University of Berlin to study pharmacy (including chemistry and botany). The next year he passed the state pharmaceutical examination and in November 1881 was licensed to practice. However, first he had to complete his compulsary military service, during which he worked as a voluntary military pharmacist in Berlin. Meanwhile he conducted research on the mechanical protection of seeds, under the botanist Professor S. Schwendener,and in March 1883 was awarded the degrees Master of Arts (MA) and Doctor of Philosophy (Dr Phil) by the University of Rostock, the latter for his thesis Die mechanischen Schutzmiddel der Samen gegen schaedliche Einfluesse von auszen. The thesis was published in A. Engler's Botanischer Jahrbuecher that same year.
Marloth then emigrated to the Cape Colony and in December 1883 started work as a chemist for the firm Wentzel and Schleswig of Cape Town. He was registered to practise as a pharmacist at the Cape in August 1884. At the time of his arrival in South Africa he was the only person with an all-round botanical training in the country, yet he never held a paid appointment as a botanist. From November 1885 to February 1886 he managed a pharmacy in Kimberley. In 1889 he opened a private analytical laboratory in Burg Street, Cape Town, where he practised as a consulting analytical chemist. The laboratory was destroyed by fire in 1892, but re-opened in Church Street, where he carried out chemical and botanical work until his death. During the 1890's he also presented correspondence courses in pharmacy under the name "School of Pharmacy".
Immediately after his arrival in Cape Town Marloth started collecting plants in his spare time, for his own herbarium. His early collecting trips to regions that warranted further botanical exploration, usually by ox-waggon or horse-drawn cart, included the Kimberley area (November 1885 to February 1886) and Damaraland in Namibia (April to June, 1886). The plants he collected in Namibia were described by A. Engler in his Botanischer Jahrbuecher in 1888-1890. During 1887 to 1889 he collected on the Great Winterhoek peak near Tulbagh, at Michell's Pass, Stellenbosch, and the Knysna forests. Visits to the Matroosberg in 1893 and 1895 produced 20 new plant species, while in 1896 at Jonkershoek he discovered the Wild Gloxinia, describing it in 1898 as a new genus and species, Charadrophila capensis.
The University of the Cape of Good Hope admitted him to the MA degree in 1888, on the basis of his degrees from the University of Rostock. That same year he was appointed lecturer in chemistry and experimental physics at Victoria College, Stellenbosch, and the next year was promoted to professor. He gave up this post in December 1891 and from 1893 until December 1903 was a part-time lecturer in science (agricultural chemistry and botany) at the Government School of Agriculture and Viticulture at Stellenbosch (from 1898 at Elsenburg). In July 1891 he married Marian van Wyk of Clanwilliam. They eventually had three sons. Marloth became a naturalised South African citizen in 1912.
During 1898-1899 the Deutsche Tiefsee-Expedition, led by Professor Carl Chun* and including the botanist A.F.W. Schimpers*, visited the Cape. Marloth and Schimpers travelled to Knysna and the Montagu and Swartberg passes. Shortly afterwards he went on his first visit to Germany. After Schimpers's death in 1901 Marloth was asked to describe the phytogeography of the Cape as part of the expedition's report. For this purpose he visited various regions of the subcontinent during the next few years, including present Zimbabwe (1903). The expedition's scientific findings were published in Wissenschaftliche Ergebnisse der Deutschen Tiefsee-Expedition auf dem Dampfer "Valdivia", 1898-1899 (1908). Marloth's contribution was titled Das Kapland, insonderheid des Reich der Kapflora, das Waldgebiet und die Karroo, pflanzengeographisch dargestellt. It was his most important contribution to plant geography. Based on his comparative study of the distribution of species he recognized the winter rainfall region between Vanrhynsdorp and the Gamtoos River as a separate floral kingdom. The rest of South Africa he divided into five floral provinces, describing the new Cape kingdom, and the forests of the south coast and the central province in detail. He also dealt with matters such as the relationship between plant communities and their environment, the adaptation of species, and the origins of the Cape flora. It was a pioneer work, remarkable for its breadth and modernity of outlook and the range of knowledge it displayed, and remained the most comprehensive work on the plant geography of the Cape for decades.
In later years Marloth again visited Namibia, collecting plants and other natural history specimens on the diamond fields (November 1908), around Luderitz (August 1909) and at Aus (October 1910). He presented various specimens to the South African Museum, for example some spiders (1898), beetles collected at high altitudes in the Western Cape (1899), five species of Euphorbia (1908), and some scorpions (1897) and reptiles (1909) from Namibia. His collecting trips to various regions of the Cape Province continued until his death in 1931. Primarily a field botanist, his knowledge of the Cape flora in the field was unsurpassed, though his collecting was sometimes inadequate. It was the living plants that he studied, either in the wild or in his private botanic garden.
In 1918 he became a member of the first advisory committee of the Botanical Survey of the Union of South Africa, and was appointed director of the Botanical Survey of the Western Cape in 1927. Though he was not a true systematist he published a number of descriptions of South African plants and some papers on their classification. However, most of his work dealt with phytogeography, ecology, plant anatomy, and the adaptation of plants to their environment. He gave particular attention to local succulents, discovering and describing many new species. In his later years he encouraged A.G.J. (Hans) Herre and Professor G.C. Nel to collect, grow and study succulents at Stellenbosch.
The publication for which Marloth is most widely known is his Flora of South Africa (4 vols, 1913-1932). This beautifully illustrated work contains a short description of each plant family, a key to the genera of each family, and information on the adaptation of species to climate, soil and herbivores. The work reflects his unbounded enthusiasm for the rare and wonderful in plant life and contains numerous original observations on the biology of plants. It constitutes a most valuable contribution to informal education in South African botany. He also collected Dutch and Afrikaans vernacular plant names, which were published in the form of a Dictionary of the common names of plants... (Cape Town, 1917).
Marloth became a member of the South African Philosophical Society in 1885. The papers that he read at its meetings, and that were published in its Transactions, included "On the origin of the diamond mines of South Africa" (1887), "Some adaptations of South Africal plants to the climate" (1890), "The acacias of southern Africa" (1893), "The progress of natural science in South Africa during the last ten years" (1895), "Means of the distribution of seeds in the South African flora" (1896), "The origin of nitrates in Griqualand West" (1896), "Occurrence of alpine types in the vegetation of the higher peaks of the south-western region of the Cape" (1901), "Mimicry among plants" (1904, 1905), "Observations on the function of the ethereal oils of Xerophytic plants" (1906), and "Some new South African succulents" (1907). After the society became the Royal Society of South Africa in 1908 he contributed, among others, the following articles to its Transactions: "Notes on the absorption of water by aerial organs of plants" (1908/10), and "Notes on the entomophilous nature of Encephalartos" (1914/5).
As a foundation member of the South African Association for the Advancement of Science he regularly read papers at its annual congresses and these were published in the association's annual Report and its successor, the South African Journal of Science. For example, "The historical development of the geographical botany of southern Africa" (1903), "Notes on the vegetation of Southern Rhodesia" (1904), "On some aspects in the vegetation of South Africa which are due to the prevailing winds" (1906), "Some observations on entomophilous flowers" (1907), "The plant formations of the Cape Province" (1908), "The vegetation of the southern Namib" (1909), "Notes on the origin of the diamonds of German South West Africa" (1909), "Notes on the determination of the acidity of soils" (1924), "Notes on the question of veld burning" (1924), and "A revision of the group Virosae of the genus Euphorbia as far as represented in South Africa" (1930). In Engler's Botanischer Jahrbuecher he published "Das suedoestliche Kalahari-Gebiet: ein Beitrag zur Pflanzen-Geographie Sued-Afrikas" (1887). Other papers dealt with "The chemistry of South African plants and plant products" (Presidential address to the Cape Chemical Society, Cape Town, 1913); and "Stone-shaped plants" (South African Journal of Natural History, 1929). In "Die Schutzmittel der Pflanzen gegen uebermaessige Insolation" (Berichte der Deutsche Botanische Gesellschaft, 1909) he first drew attention to succulents with window leaves. In one of his experiments he established that the parasitic barnacle Tubicinella trachealis penetrates the skin of its host, the Southern Right Whale, by chemically dissolving it (1900). In other experiments, conducted on Table Mountain, he estimated the quantity of water condensed from clouds and published the results in the Transactions of the South African Philosophical Society for 1903 and 1905.
Marloth was the first examiner in botany at the BA and BA (Hons) level for the University of the Cape of Good Hope, setting papers in 1888 and 1897-1900. At the request of the superintendent-general of education at the Cape, Sir Thomas Muir* he adapted H. Edmond's text-book on botany to produce Elementary botany for South Africa, theoretical and practical (Cape Town, 1897, with several later editions). It was the first textbook to use local examples in explaining the morphology, systematics and ecology of plants. His other interests included graphology (the study of handwriting), a topic on which he gave evidence in the courts as an expert witness during the nineteen-twenties. Furthermore, his presidential address to the Cape Chemical Society in 1925 dealt with the chemical analysis of handwriting to detect forgery. He was an indefatigable walker, often out from very early in the morning or until late at night, and played a prominent role in the formation of the Mountain Club of South Africa in 1891. As an expert photographer he produced many of the photographs used to illustrate his publications. He was a thin, fairly tall person, quiet and unassuming, a true individualist, known for his perseverance and hard work. However, he could not tolerate laziness and lack of discipline and his quick, direct way of speaking sometimes made him seem discourteous. One of his students and a life-long friend was the statesman and amateur botanist J.C. Smuts*.
Marloth served as president of the South African Philosophical Society (1893-1895) and in 1908 became one of the original Fellows of its successor, the Royal Society of South Africa. He was president of the South African Association for the Advancement of Science in 1914, of the Cape Chemical Society in 1909, 1913 and 1925, and of the South African Biological Society in 1929; Chairman of the Mountain Club of South Africa from 1900 to 1906, and of the Suid-Afrikaanse Akademie vir Wetenskap en Kuns in 1915.
He received various honours during his lifetime: The German Roter Adlerorden (Order of the Red Eagle, 1910), the South Africa Medal (gold) of the South African Association for the Advancement of Science (1914), an honorary Doctor of Science (DSc) degree from the University of Stellenbosch (1922), the Captain Scott medal of the South African Biological Society (1923), honorary life membership of the Deutsche Botanische Gesellschaft (1925) and of the Botanical Society of South Africa (1926), the Gustav Nachtigal medal of the Gesellschaft fuer Erdkunde, Berlin (1928), honorary doctorates from the Universities of Heidelberg and Cape Town (1929), and honorary membership of the Austrian Botanical Society (1930). He died as the result of a stroke.
Three genera of South African plants, Marlothia, Marlothiella and Marlothistella, as well as several species such as Aloe marlothi and Euphorbia marlothi, were named in his honour. His herbarium collection of some 15 000 sheets was presented to the National Herbarium in Pretoria in 1927. Duplicates are in the Bolus Herbarium, Albany Museum, at Kew Gardens, the University of Stellenbosch, and in Berlin. His photographic negatives, letters, collection registers, documents and mineral collection are housed in the Marloth Collection of the University of Stellenbosch.