Jordan, (Claude Thomas) Alexis

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Jordan, (Claude Thomas) Alexis

(b. Lyons, France, 29 October 1814; d. Lyons, 7 February 1897)


Jordan belonged to one of the most distinguished families of the Lyons bourgeoisie. His father, César, was a rich merchant; his mother, Jeanne-Marie (called Adèle) Caquet d’Avaize, was the daughter of a lawyer. Camille Jordan, the writer and politician, was his uncle and the mathematician Camille Jordan was a cousin. A Catholic and a royalist, Jordan was a member of the Société Botanique de France, the Imperial Society of Naturalists of Moscow, and the Royal Botanical Society of Belgium, among others.

Only botany could induce Jordan to leave Lyons. He received his secondary education there and, renouncing a career in commerce, turned to the natural sciences. He frequented a group of cultivated amateurs who enlivened the Linnaean Society of Lyons and he soon specialized in botany under the direction of Nicolas Seringe, a military surgeon who became director of the Lyons Botanical Garden and whose assistant he was for a time.

Apparently Jordan’s task originally was purely descriptive and modest: to complete or correct the existing French floras on certain points. Between 1836 and 1846 he was essentially an observer and a researcher in the field. Each year he made several long botanical journeys, usually beyond the southeast but rarely outside of France (except to Corsica and Italy). These trips and the samples sent him by the many botanists with whom he corresponded allowed Jordan to assemble one of the most important private herbaria in Europe. His personal fortune enabled him to amass a library and experimental equipment comparable with those of the great professional botanists of his time.

Between the ages of twenty-five and thirty, Jordan concentrated on certain plants difficult to classify that had been brought to his attention by his friend Marc- Antoine Timeroy. These plants did not coincide exactly with the descriptions of the floras, and yet they could not be treated as simple varieties. Jordan soon became convinced, on these grounds, that the classic method of description itself was too schematic: a single species name was almost always applied to a multiplicity of forms that were quite similar, yet distinct and stable. This was particularly the explanation of the so-called polymorphous species, to which the very special faculty of “varying” was attributed. As early as 1846 Jordan concluded that at least five “easy to distinguish although very closely related” species are designated by the name Viola tricolor L. (the pansy); each of them, moreover, proves to be invariable after several years of cultivation.

Jordan announced these general conclusions in 1846 and 1847 to the Linnaean Society of Lyons in a series of seven monographs entitled Observations sur plusieurs plantes nouvelles rares ou critiques. From then on, the concept of species itself was in question. Beginning in the 1850’s, Jordan became a theoretician and virtually chef d’éole. The Linnaean notion of species corresponded, according to him, not to the real boundaries of the plant forms but to a crude division suggested by simple, practical convenience: it retained only those characteristics that are easily distinguished with the naked eye by a botanist of average experience and that are preserved when the plant is dried in a herbarium. Experiment shows that a great many essential traits are not necessarily of this sort. Furthermore, the rigorous invariability of the species, largely underestimated by classical botanists, is confirmed by the facts and is already contained in the pure concept of species in general, which is logically prior to experiment and is the basis on which experiment can be methodically conducted and interpreted. “The observer who wishes to proceed on sure ground. . .should take philosophy for his guide and theology for his compass” (Remarques. . .p. 23). Every authentic being was “conceived by thought as absolutely one and indivisible. . .as immutable and unalterable” in that which is proper to it (De l’origine . . ., p.5). The living species was a being of this kind: its “substantial” character was confirmed by its permanence during the course of generations, and every type that showed itself to be variable in its lineage was hybrid. Varieties, properly speaking, originate among the plants from superficial, environmentally determined modifications, which are not transmitted to the descendants; they do not affect the “substance” of the species.

This break with traditional concepts necessitated a change in method. “Closely related” species (espèces affines) exist everywhere; a given species, Jordan noted, was almost always surrounded, in a single location, by several analogous forms. All the true species could be counted only by controlling the descendants, that is, by cultural experimentation. Giving up his botanical expeditions, Jordan now limited his activity as an investigator to his experimental garden; the first one measured only about 400 square meters. About 1850 an inheritance from an uncle enabled him to buy a plot at Villeurbanne that he gradually increased to 12,000 square meters. At its best it had about 400 flower beds, grouped in equal squares and containing approximately 50,000- 60,000 plants. A series of related forms belonging to the same Linnaean species was placed in the same flower bed, and their complete stability from year to year was verified. Thus, twenty-five kinds of Scabiosa succisa, thirty-five of Sempervivum tectorum, and so on, coexisted without ever intermingling. The record was established by Draba verna (a crucifer with rosette leaves and small flowers that is frequently found in spring on walls and embankments), from which as many as 200 distinct forms were obtained. These “genuine species” were distinguished not by a major difference limited to one characteristic (Jordan considered the sudden modifications that sometimes disturb a characteristic in a line to be an accident, a lusus naturae that may be disregarded) but rather by a series of small but very stable details: for example, by bifurcated or trifurcated hairs, petals that are more or less narrow, fruits varying in size in relation to the length of the stem, and so on.

Yet if true species are rigorously invariable, how can one interpret the effects of cultivation, which seems to create and determine the quantity of new forms? In reply to this question Jordan published De l’origine des diverses variétés ou espèces (1853). In fields, gardens, and orchards, he explains, many plants may be seen that were unknown, say, in the seventeenth century. But either they are purely individual variations due to the environment—and it is the permanence of this environment, not heredity, that creates the uniformity of the successive generations—or else it is a question of true species; but then they are new only for us, since they already existed in earlier times.

Jordan’s career—he was both a bachelor with a difficult nature and an increasingly intransigent theorist—ended in growing isolation. In 1864 he entrusted the management of his garden to Jules Fourreau. Some deplored the influence that Fourreau immediately began to exact on him: he was more Jordanian than his master. He incited Jordan, it was said, to multiply species without limit by arbitrarily purging his flower beds in order to make the lines more homogeneous, sometimes dispensing with the cultural criterion in the process. Jordan maintained this orientation after Fourreau’s death. The last years of this obstinate monarchist saw his involvement in a naïve political enterprise that estranged a great many of his former friends.

When Jordan died, his reputation was at its lowest ebb. The conservative botanists reproached him for “pulverizing” the species and ruining systematics; on the other side, a triumphant Darwinism drew the younger botanists away from this “ultra” of fixity. Nevertheless, French and foreign researchers repeated certain of his experiments and were able to confirm them. Beginning in 1900 it was, paradoxically, the neo-Darwinians who rediscovered the radical separation of hereditary characteristics and variations due simply to the environment and who emphasized the idea that the Linnaean species is only a convenient category, a subgroup in a discontinuous series of elementary types. Hugo de Vries reappraised Jordan’s work, reinterpreting it in terms of mutation; and in 1916 J. P. Lotsy introduced the term “Jordanson,” in opposition to “Linneon,” in order to designate the species in Jordan’s sense.

Thus, Jordan’s fixity, now completely outdated, survives only in the conclusions that this unusual theorist drew and confirmed from it: the intransmissibility of acquired characteristics and the traditional concept of species considered as the blending of separate but closely related homogeneous types, since they appear genetically stable at first consideration. And the lusus naturae or mutations that he eliminated from botany have become for contemporary biology a way of conceiving of the origin of “Jordanon species.”


I. Original Works. Jordan’s works in systematic botany include Observations sur plusieurs plantes nouvelles rares ou critiques, 7 pts. (Paris, 1846-1847); Pulillus plan-tarum novarum praesertim gallicarum (Paris, 1852); Diagnoses d’espéconnues pour servir de matériaux à une flore réformée de la France et des contrées voisines (Paris, 1864); and his masterwork, Icones ad floram Europae nove fundamento instaurandam spectantes, 3 vols. (Paris, 1866-1903), written with J. Fourreau.

His theoretical writings include De l’origine des diverses variétés ou espéces d’arbres fruitiers et autres végétaux généralment cultivéves les besoins de l’ homme (Paris, 1853); and Remarques sur le fait de l’existence en société ã L’état sauvage des espéces végeacute;tales affines et sur d‘ autres faits relatifs ã la question de l’espéce (Lyone, 1873). There is also the critical study“Rapport sur l’ Essai de phytostatique appliquée ã la chaine du Jura et aux contrées voisines par M. Thurmann“, in Annales des sciences physiques et naturelles, de’agriculture et d’indusrie publiées par la Société nationale d’agriculture, d’histoire naturelle et des arts utiles de Lyon (1850), pp. 7-30.

II. Secondary Literature. An excellent source is C. Roux and A. Colomb, “Alexis Jordan et son oeuvre botanique”, in Annales de la Sociéenne linneenne de Lyon, n.s. 54 (1908), 181-258. See also A. Magnin,Prodrome d’une histoire des botanistes lyonnais (Lyons, 1906), pp. 97-107; and Viviand -Morel, “Histoire abrégée des cultures expérimentales du jardin d”A. Jordan, “in Lyon horticole et horticultales nouvelle (1907), nos. 3, pp.57/-59; 4, pp.77-78; 7, pp. 137-140; 21, pp. 415-. Recent studies on Jordan’s thought are M. Breistoffer, “Sur la nomenclature botanique de quelques botanistes lyonnais”, in Comptes rendus du 89° Congrétés savantes (Paris, 1965); and J. Piquemal “Alexis jordan et la nation d’espéce”, Conférences du Palais de la découverte (Paris, 1964).

Jacques Piquemal