by Neus Ibáñez, Botanic Institute of Barcelona, IBB, CSIC-CMCNB
Jean Odon Debeaux (Agen, 1826 — Toulouse, Languedoc, 1910) was a military pharmacist and Occitan botanist. Posted to Perpignan (1872-80), he studied the flora of Northern Catalonia, in particular the genus Rosa. Later, when he established in Toulouse, after his retirement in 1886, he collaborated with Carles Pau Espanyol (1857-1937), one of the most important botanist in Spain at that time.
The herbarium of Debeaux is primarily conserved in the Paris Herbarium (P), though duplicate specimens can be found in numerous other herbaria worldwide. In addition to his extensive plant collections, Debeaux also compiled exsiccatae, including a series dedicated to Corsican plants, which is preserved in the Geneva Herbarium (G), and another on Plantes de l’Algérie (1880–1883).
Our study focuses on Algerian plant specimens collected by Debeaux and conserved in both the Angers Herbarium (ANG) and the Botanic Institute of Barcelona Herbarium (BC). During our secondment at the Angers Herbarium in October 2024, we examined a total of 98 Algerian specimens collected by Debeaux and housed at ANG. Among these, only 11 specimens have duplicates preserved in BC, with collection dates ranging from 1874 to 1884.
Among the specimens examined, we highlight several herbarium vouchers of Coronilla pentaphylla Desf., gathered by Debeaux from “au dessous du fort Santa Cruz” (Oran) on April 12 and June 14, 1883. These specimens, gathered at the same time and at the same place, are currently conserved in the herbaria of Meise Botanic Garden (BR), Angers (ANG), and the Botanic Institute of Barcelona (BC) (Fig. 1–2).

Fig.1. Duplicates of Coronilla pentaphylla Desf. (A) ANG080132, (B) BR0000029492343 (C) BR0000029492404, (D) BC-16786, collected by Debeaux in Santa Cruz (Oran)
One of the specimens preserved in BR (BR0000029492367) has been identified as the original collection. This conclusion is based on the presence of Debeaux’s handwritten label, which does not bear the heading of Flora Selecta Exsiccata (Fig. 2), confirming its authenticity as a primary specimen directly handled and labelled by Debeaux himself.

Fig.2. Original specimen of Coronilla pentaphylla collected by Debeaux in Oran and conserved in Meise Botanic Garden (BR0000029492367)
In contrast, four additional specimens have been identified as duplicates of this original collection. These duplicates are labelled with the heading of Flora Selecta Exsiccata, a collection curated by Charles Magnier (1853-?), a French botanist which his main herbarium is conserved in Natural History Museum of Besançon (https://www.recolnat.org/en/nos-partenaires/les-herbiers-du-museum-dhistoire-naturelle-de-besancon). These labels suggest that these plants were selected and distributed as part of this prestigious botanical series. Assigned the number 552 within the Flora Selecta Exsiccata, these specimens were circulated across European herbaria due to their botanical significance. The purpose of this exsiccatae, as described by Bornet & Malinvaud (1885), was “destinée à répandre dans les herbiers les plantes rares d’Europe et à fournir des matériaux d’études pour les genres difficiles et riches en formes litigieuses.” The Flora Selecta Exsiccata was commercialized at prices ranging from 27 to 62 francs per fascicle (Nualart, 2024), making it accessible to European researchers and institutions.
The creation of exsiccatae collections, particularly in the 19th century, was a pivotal practice in botanical science. These collections served as critical scientific resources, with each specimen carefully identified and validated by prominent botanists. As a result, they were regarded as reference materials for taxonomic and floristic studies, providing reliable documentation for plant identification and classification (Bange, 2012; Gavioli et al., 2024).
Our study provides a clear example of how this Algerian taxon was disseminated throughout Europe via the Flora Selecta Exsiccata, playing a crucial role in the circulation of botanical specimens and scientific knowledge at a continental scale. Through this systematic distribution, knowledge of Coronilla pentaphylla, first described by René Louiche Desfontaines (1750–1833) from Algeria in 1779 (Desfontaines, 1779), extended beyond its region of origin to Spain, Belgium, and France. This case illustrates the broader impact of 19th-century botanical networks in shaping the taxonomic and floristic understanding of Mediterranean flora
Another taxon we have studied is Sideritis guyoniana var. angustifolia, a variety described by O. Debeaux. This subshrub, native to Algeria, thrives primarily in subtropical biomes. The herbarium specimens examined for this taxon were collected from Djebel Santo (Oran) on June 13, 1883. We have analysed two specimens: one conserved in the Angers Herbarium (ANG) under the accession number ANG077770 (Fig. 3) and the other in the Botanic Institute of Barcelona Herbarium (BC) under BC-73230 (Fig. 4).


Fig.3. ANG077770
Fig.4. BC-73230
The specimen conserved in ANG is a duplicate, distributed in 1885 through the Société Dauphinoise with the number 4643, as indicated by the heading on its label. The Société Dauphinoise pour l’échange des plantes d’herbier (1873-1892) was founded in Grenoble by Jean-Baptiste Verlot (1816-1891), director of the city’s Jardin des Plantes, Casimir Arvet-Touvet (1841-1913), and Joseph-Pamphile Faure (1835-1896) (Gavioli et al., 2024). This societies of exchange of plants facilitated the exchange of specimens between nation-states in Europe in the 19th century and offered the possibility of connecting with foreign botanists, allowing them to weave exchange networks to obtain specimens from regions that were difficult to collect or specimens belonging to taxonomically complex generaIn this case, the specimen housed in BC, represents the original collection. This determination is based on its handwritten label by Debeaux and the presence of a botanical sketch illustrating the narrow (angustifolia) leaf— the defining characteristic of this variety (Fig. 4). Furthermore, the label indicates that this specimen was previously part of the Herbier de l’Afrique du Nord, housed at the University of Algeria.
The description of Sideritis guyoniana var. angustifolia was officially published by Debeaux in Notes sur quelques plantes rares ou peu connues de la flore oranaise (1888). In this work, he noted the existence of two varieties in the Oran region: one with broad (latifolia) leaves, described by Boissier and Reuter from the locality known as Batterie Espagnole, and a second variety with narrow (angustifolia) leaves, which he observed in Djebel Santo—the locality where the BC specimen was collected (Fig. 5).

Fig. 5. Notes sur quelques plantes rares ou peu connues de la flore oranaise by Debeaux (1888), pg. 312, published by O. Debeaux
This taxonomic variety remained in use for several decades. The Spanish botanist Pius Font Quer (1888–1964), a leading specialist in the Sideritis genus, referenced Sideritis guyoniana var. angustifolia in his work Estudis sobre morfologia i nomenclatura de les Sideritis (Secció Eusideritis Benth.) (Font Quer, 1924) (Fig. 6). Additionally, herbarium specimens collected in later years continued to recognize this variety as valid. For instance, the BC-73228 specimen, collected from Algeria in 1914 by Alphonse Faure (1865–1958), was annotated as Sideritis guyoniana var. angustifolia (Fig. 7), reflecting its on-going acceptance within the botanical community.
Through this study, we have demonstrated that Debeaux was not only an important botanist but also a key figure in the dissemination of North African plant specimens throughout Europe. His taxonomic contributions, including the description of new Algerian taxa, had a lasting impact, with some of his classifications remaining in use for decades and being referenced by later specialists.

Fig.6.“Estudis sobre morfologia i nomenclatura de les Sideritis (Secció Eusideritis Benth)”. Trabajos del Museo de Ciencias Naturales de Barcelona, vol. 5 (Série Botánica, núm. 4) published by Font i Quer in 1924.


Fig. 7. BC-73228
In conclusion, Debeaux’s research on Algerian flora significantly contributed to the understanding of the region’s biodiversity. His collections and taxonomic insights facilitated the dissemination of botanical knowledge across a broad network of European scientists, reinforcing the interconnected nature of botanical exploration and taxonomy in the 19th and early 20th centuries.
References cited
Bange, C. (2012). Travail collectif en botanique et validation scientifique : les sociétés d’échange de plantes. Bulletin d’histoire et d’épistémologie des sciences de la Vie 19 (2): 175-189.
Bornet, E. & Malinvaud, E. (1885). Nouvelles. Bulletin de la Société botanique de France 32: 48.
Debeaux. O. (1888). Notes sur quelques plantes rares ou peu connues de la flore oranaise. Association française pour l’avancement des sciences. Congrès d’Oran 1888. Paris. https://gallica.bnf.fr/ark:/12148/bpt6k201169f/f305.item#
Desfontaines, R.L. (1799). Flora Atlantica: sive historia plantarum quae in Atlante, agro tunetano et algeriensi crescunt. Parisiis
Font i Quer, P. (1924). Estudis sobre morfologia i nomenclatura de les Sideritis (Secció Eusideritis Benth). Trabajos del Museo de Ciencias Naturales de Barcelona, 5 (Série Botánica, núm. 4), 35 p. https://museucienciesjournals.cat/other/tmcnb/volum-v-botanica/estudis-sobre-morfologia-i-nomenclatura-de-les-sideritis-seccio-eusideritis-benth-museo-de-ciencias-naturales-trabajos-del-museo-de-ciencias-naturales-de-barcelona-serie-botanica-4
Gavioli, L., Nualart, N., López-Pujol, J., Catalá-Gorgues, J. I. & Ibáñez, N. (2024). Redes y sociedades de intercambio en el siglo XIX a través de las exsiccatae del herbario Trèmols. Dynamis 44(2): 383-414. http://dx.doi.org/10.30827/dynamis.v44i2.31695
Nualart, N. (2025). The difficulties of taxonomic attribution at the end of 19th Century: Saxifraga hervieri as a case study. SciCoMove — Scientific Collections on the Move. Retrieved February 10, 2025 from https://doi.org/10.58079/134s1