CAMERARIUS (CAMERER), RUDOLPH JAKOB

(b. Tübingen, Germany, 12 February 1665; d Tübingen, I 1 September 1721)

medicine, botany.

Camerarius was the older son of Elias Rudolph Camerarius (1641–1695), professor of medicine, and grandson of Johann Rudolph Camerarius (1618 – 1675), a physician. After earning his bachelor’s (1679) and master’s (1682) degrees, he traveled through Germany, Holland, England, France, and Italy from 1685 to 1687. Following his return to Tübingen, he received the doctorate at the university in 1687 and in 1688 was appointed extraordinary professor of medicine there and director of the botanical gardens. Upon the death of his father in 1695, Camerarius succeeded him as full professor. He died in 1721 of tuberculosis.

Camerarius’ most important scientific achievement was the experimental demonstration of the sexuality of plants. This fundamental biological question had been debated by Theophrastus and, later, by Cesalpino (1583), Malpighi (1675), and Grew (1682), among others; but no clear conclusion had been reached. Camerarius was the first to prove by numerous experiments that sexuality must be attributed to plants. He reported his findings on the subject in the customary form of a long letter, Epistola . . . de sexu plantarum, which he sent in 1694 to Michael Bernhard Valentini, professor of medicine at Giessen, and which was subsequently printed several times. In it Camerarius first described, with great clarity, the structure of the flower in its various forms. Next he carefully compared plant and animal reproduction, drawing upon his own observations and experiments, some of the results of which he had already published. He had observed, for example, that a female mulberry tree (Morus) bears fruit even though no male tree is near it. The berries, however, contain only empty seeds, which he compared to the unfertilized “wind eggs” of the chicken.

After making this discovery, Camerarius conducted his first experiment with another dioecious plant, Mercurialis annua (1691), setting two female plants in flowerpots and isolating them from other plants. They produced fruit, but it soon dried up and contained no seeds. He repeated the same experiment with two other dioecious plants: Spinacia oleracea and Cannabis sativa. Turning his attention to the monoecious plants Ricinus communis and Zea mays, Camerarius cut off the male inflorescences below the opening of the anthers; in these cases, too, only empty fruit was produced. From these experiments Camerarius concluded that the anthers represent the male organs of the plant and the ovary, with style and stigma, the female organs. He considered those plants in which male and female organs coexist in the same flower to be hermaphroditic, and compared them with the snails, the hermaphroditism of which had been discovered shortly before by Swammerdam. Camerarius’ assumption that the hermaphrodite plants, in contrast with the snails, fertilized themselves, later proved to be incorrect; Joseph Gottlieb Kölreuter (1761) and Christian Konrad Sprengel (1793) showed that allogamy predominates among hermaphrodites.

Camerarius further displayed his critical powers as a researcher by raising several objections to his view. He pointed out, for example, that Lycopo-dium and Equisetum form only flowers with many anthers, but that “they lack a female sex.” The reproduction of these plants was not elucidated until a century and a half later, by Wilhelm Hofmeister. Camerarius also saw a serious challenge to his views in the fact that during his experiments, an ear of corn on a castrated plant had produced several fertile kernels, even though the intact plants were far away. In addition, he had encountered a similar phenomenon in experiments on Cannabis. Valentini wrote to Camerarius. in his response to the Epistola, that these last cases can be attributed to pollen having been carried by the wind over long distances.

Camerarius’ experiments were confirmed at the Berlin Botanical Gardens in 1749. There, Johann Gottlieb Gleditsch induced a female palm tree (Chamaerops humilis) to produce seeds by dusting it with pollen obtained from a male specimen in the Leipzig Botanical Garden. Gleditsch repeated this experiment in 1750 and 1751 with equal success.

Camerarius had shown that ripe seeds form only if the stigma has been covered with pollen. The fact that the pollen also plays a role in the structure of the subsequent generation was demonstrated, however, by Kölreuter (1761) through the creation of numerous hybrids, among which could be detected various combinations of characteristics derived from the male or from the female parent. Nevertheless, many botanists continued to deny the sexuality of plants until the beginning of the nineteenth century. Finally, the works of Karl Friedrich von Gaertner (1844, 1849), who carried out over nine thousand hybridization experiments, overcame the last doubts on the matter.

In addition to the Epistola . . . de sexu plantarum Camerarius published about thirty other, mostly briefer, works on botany. In the most notable of these. De convenientia plantarum in-fructifi-catione et viribus (1699), he showed that plants displaying similar flower structures possess similar healing properties {vires) and. therefore, are constituted of similar substances. This notion, which Linnaeus, referring to Camerarius, later discussed in his Philosophia hotanica (1751), has been thoroughly confirmed by modern chemotaxonomical methods.

BIBLIOGRAPHY

I. Original Works Epistola ad D. Mich. Bern. Valentini de sexu plantarum(Tübingen, 1694) was also published in Johann Georg Gmeltn, Sermo academicus de novorum vegetabilium . . . exortu (Tübingen, 1749), 83–148; and in Johann Christian Mikan, Opuscula bataniei argumenti (Prague, 1797), 43–117. It was translated into German, with extensive commentary and complete bibliography, by Martin Möbius as no. 105 in Ostward’s Klassiker der Exakten Wissenschaften (Leipzig, 1899). Also see De convenientia plantarum in fructijkatione et virihus (Tübingen. 1699).

II. Secondary Literature See Alexander Camerarius. “Memoria Camerariana comprehendens pro-gramma funebre B, Rud. Jac. (amerarii.”) in Acta Physico-Medica Exhihentia Ephemerides, 1 (1727). app.. 165–183; L. W. O. Camerer and J. F. W. Carnerer, Geschichte der Tübinger Familie Camerer 1503–1903 (Tübingen, 1903); A. Hirseh, ed., Biographisches Lexi-kon der hervorragendsten Änte alter Völker and Zeitvn, I (1929), 808–809, and supp. (1935). 155; K. Mäigde-frau, Geschiclue der Botanik(Stuttgart, 1973). 108–111; J. Mayerhöfer, Lexikon der Geschiclue der Naturwissenschaften, I (Vienna, 1958). 595; J. Sachs, Geschiclue der Botanik (Munich. 1875), 416–421: andWorld Who’s Who in Science (Chicago, 1968). 291.

Karl MÄgdefrau