German plant collector in North America and Mexico. Carl Purpus was born in Hanweilerhof in southwest Bavaria, the son of a forester. After a youth spent roaming the forests and mountains of the locale and exploring farther afield in Switzerland and northern Italy, he trained as a pharmacist, studying at Giessen in 1876-1877. His life's work, however, would be botanical collecting, recalling his early love of gathering alpine plants.

Perhaps influenced by his father, who had charge of the royal forests of Bavaria, Purpus was recruited with his younger brother Joseph (a horticulturalist who joined the Botanic Garden of St. Petersburg in 1882) on a mission to collect winter-hardy plants in North America for an arboretum in Zoeschem. In 1887 the brothers thus joined forces and sailed to North America. While the younger Purpus followed up their plant collecting activities with a year working in an Ohio garden before re-crossing the Atlantic, Carl Purpus decided to stay permanently in America. Indeed, he only saw Europe once more in his life when he made a visit to Germany, Belgium and Italy in 1904.

Over the three years following his arrival in the New World he collected plants in the Rocky Mountains and the northwest states, moving down the coast to California, Nevada and Arizona in the early 1890s. He made a living by selling seeds, cacti and pinecones to German dealers and also offering sets of herbarium specimens, chiefly to Berlin, where K. Schumann studied his cactus specimens. Occasionally he published descriptions of the American landscapes in the German periodical Ausland. He also gave specimens to Katharine Brandegee, a San Diego botanist, for determination. Brandegee was recommended to Purpus by the ornithologist Charles Keeler, with whom he had become acquainted. On meeting the Californian botanist a long-lasting relationship began between the German collector and both Katherine and her husband, Townshend Brandegee, also a botanist. Together they went collecting in Baja California in 1897-1898, visiting the islands of San Martín and San Jerónimo, the mining camp Calmallí and the area around San Pablo, and volcanic peaks to the east of an old Jesuit mission, Santa Gertrudis. Taking back 15 boxes of cacti and other succulents to California, Purpus sent most of his specimens, as usual, to Germany.

Continuing to collect in the south-west U.S. over the following years he returned to Mexico several times from 1900-1905, taking in Sinaloa and the volcanic zone of Ixtaccíhuatl and Popocatépetl, and developing an deep affection for the country, whose dry mountains yielded such different flora to that of the Alps in his wanderings of yore. In 1905 he was welcomed at Hacienda Zacuapam, which belonged to Florentin Sartorius, son of the botanist Carl Sartorius. Purpus made this hacienda (near Huatusco, Veracruz) his home for the rest of his days. He became an official collector for the University of California, where his erstwhile co-collector, Townshend Brandegee, was by then employed at Berkeley. Katherine Brandegee, meanwhile, was the first female curator at the California Academy of Sciences Herbarium. Townshend Brandegee both determined Purpus’ specimens and arranged for duplicate sets to be sold, the profits going to Purpus. Purpus sent regular shipments to Berkeley up until Brandegee's death in 1925, after which he sent fewer sets. He had sent to Berkeley nearly 16,000 numbers by the time of his own death, originating from many parts of the Mexican landscape.

In 1908 Purpus was joined by Townshend Brandegee collecting in the southern states of Puebla and Oaxaca (though the American botanist's name does not appear on the herbarium sheets). His brother Joseph also visited him, bringing along the director of the botanical garden at Darmstadt, Heinrich Schenck (1860-1927). Together they went in search of succulents for the Darmstadt garden, trekking across the states of Mexico and Vercruz, but the European botanists found the demands of field work in this terrain difficult and relations between them and the much hardier Carl Purpus were strained. Adding to their discomfort, Joseph Purpus contracted malaria. He and Schenck departed from Veracruz in October that year, while Carl Purpus carried on his unceasing explorations, moving north to San Luis Potosí and Coahuila. He too, however, fell gravely ill with malaria in 1910, but went straight back to the strenuous work of collecting as soon as he was recovered.

He was also acutely aware of the dangers posed by Zapatistas and bandits, which curtailed his movements somewhat in the coming years. Others were also wary of travel in the country's backwaters. Purpus wrote to Brandegee in 1918 reporting that the U.S. agricultural explorer F.W. Poponoe, then in Mexico collecting avocado plants, would not visit him at Zacuapam for fear of being subject to attack. Some ten years later, Purpus was forced into a hiatus having not even stepped beyond his own threshold, when burglars delivered a (non-fatal) blow to his head with a machete.

At one time Purpus also found himself collecting butterflies for Robert Mueller, a lepidopterist in Mexico City who employed various local collectors. One of these, a certain Engelmann, travelled briefly with Purpus in 1912 in Veracruz. The following year Purpus made a tour of Chiapas, weaving among the German-owned coffee plantations of Covadonga, Mexiquito and Irlande, and made more collections in Oaxaca, including from the Isthmus of Tehuantepec, before reining in his wanderings due to the increasingly volatile times (the chaotic Mexican Revolution of 1910-1920 was in full swing). One account suggests that he set up a perfumery while confined to working around his home, which area he exhaustively botanised over his lifetime.

Purpus' brother Joseph visited again in 1920-1921 on a mission to collect epiphytes, ferns and cacti for Darmstadt. Fraternal relations were none too cordial by now, however, so it is unlikely they collected together. Playing more heavily on Carl's mind at this time was an archaeological artefact he had discovered (purportedly some kind of mosaic), that he was attempting to sell on to an American museum. Having had the object valued in 1920, he was nervous with worry over robbers for months before it was finally sold. It netted him $40,000.

In 1923, at the age of 72, Purpus commenced on one of his latest and most productive circumnavigations of Veracruz and Chiapas, though he lost many specimens from one trip when caught in torrential rain. After Townshend Brandegee's death in 1925, Paul Standley at the Smithsonian Institution briefly continued his series "Plantae Mexicanae Purpusianae" in the Journal of the Washington Academy of Sciences, but the volume of collections sent from the explorer diminished in his old age, though he continued to work even as an octogenarian. He died aged 90 in 1941.

Purpus had led an energetic life of unceasing botanical endeavour. As with many such dedicated workhorses, he developed a number of idiosyncrasies. He was notably ascetic, neither drinking alcohol nor smoking, and would have no relations with women. He was instead devoted to cats, of which he had more than 60 as pets by the time of his demise. Despite living in his adopted country for nearly 40 years, he never had a particularly good grasp of Spanish, being more inclined to converse with the German speaking coffee planters than local villagers. He collected around 17,000 numbers in Mexico. Taxa named after him include the Rosaceae genus Purpusia Brandegee, the cactus Mammillaria purpusii K.Schum. and the strikingly flowered epiphyte Hylocereus purpusii (Weing.) Britton & Rose.

Sources:
B. Ertter, "On the Trail, with Purpus, in California", Carl Purpus, Plant Collector in Western America:
http://ucjeps.berkeley.edu/Purpus, accessed 10 September 2009
R. Moran, 1962, Cactus and Succulent Journal of America, 34(1): 8-12
S. Schneckenburger, 2001, Ein deutscher Pflanzensammler in Amerika, Carl Albert Purpus (1851-1941):
http://www1.tu-darmstadt.de/fb/bio/bot/purpus/index.html , accessed 10 September 2009
M. Sousa, 1969, "Las colecciones botanicas de C.A. Purpus en Mexico", University of California Publications Botany, 51: 1-36.