Gleditsia J. Clayton in Linnaeus, Gen. Pl. 5: 476. 1754.

Bruneau, Anne, de Queiroz, Luciano Paganucci, Ringelberg, Jens J., Borges, Leonardo M., Bortoluzzi, Roseli Lopes da Costa, Brown, Gillian K., Cardoso, Domingos B. O. S., Clark, Ruth P., Conceicao, Adilva de Souza, Cota, Matheus Martins Teixeira, Demeulenaere, Else, de Stefano, Rodrigo Duno, Ebinger, John E., Ferm, Julia, Fonseca-Cortes, Andres, Gagnon, Edeline, Grether, Rosaura, Guerra, Ethiene, Haston, Elspeth, Herendeen, Patrick S., Hernandez, Hector M., Hopkins, Helen C. F., Huamantupa-Chuquimaco, Isau, Hughes, Colin E., Ickert-Bond, Stefanie M., Iganci, Joao, Koenen, Erik J. M., Lewis, Gwilym P., de Lima, Haroldo Cavalcante, de Lima, Alexandre Gibau, Luckow, Melissa, Marazzi, Brigitte, Maslin, Bruce R., Morales, Matias, Morim, Marli Pires, Murphy, Daniel J., O'Donnell, Shawn A., Oliveira, Filipe Gomes, Oliveira, Ana Carla da Silva, Rando, Juliana Gastaldello, Ribeiro, Petala Gomes, Ribeiro, Carolina Lima, Santos, Felipe da Silva, Seigler, David S., da Silva, Guilherme Sousa, Simon, Marcelo F., Soares, Marcos Vinicius Batista & Terra, Vanessa, 2024, Advances in Legume Systematics 14. Classification of Caesalpinioideae. Part 2: Higher-level classification, PhytoKeys 240, pp. 1-552 : 1

Gleditsia J. Clayton in Linnaeus, Gen. Pl. 5: 476. 1754.

Figs 13 , 14 , 17

Melilobus Mitch., Diss. Gen. Pl.: 37. 1769. Type: Melilobus heterophyla Raf. [= Gleditsia triacanthos L.]

Asacara Raf., Neogenyton: 2. 1825. Type: Asacara aquatica (Marshall) Raf. [≡ Gleditsia aquatica Marshall]

Garugandra Griseb., Abh. Königl. Ges. Wiss. Göttingen 24: 96. 1879. Type: Garugandra amorphoides Griseb. [≡ Gleditsia amorphoides (Griseb.) Taub.]

Caesalpiniodes Kuntze, Rev. Gen. 1: 166. 1891. Type: Caesalpiniodes triacanthum (L.) Kuntze [≡ Gleditsia triacanthos L.]

Pogocybe Pierre, Fl. Cochinch.: t. 392B. 1899. Type: Pogocybe entadoides Pierre. [= Gleditsia australis Hemsl.]

Type.

Gleditsia triacanthos L.

Description.

Large to medium size deciduous trees ( G. saxatilis was described as evergreen), usually well-armed with simple or compound thorns on trunk and branches (Fig. 13F ), sometimes thornless, especially in cultivated plants; branches with lateral brachyblasts; androdioecious (individuals with either staminate flowers or hermaphrodite flowers) or dioecious. Stipules small, inconspicuous. Leaves bipinnate, pinnate, or intermediate with one or more pinnae replaced by a leaflet, often all forms found on the same plant; bipinnate leaves, 2-10 pairs of pinnae, leaflets (1) 4-32 per pinna, lamina margins usually crenulate, rarely entire (Fig. 13E ). Inflorescences terminal, axillary or cauliflorous racemes, few to many flowered; bracts present, caducous (Fig. 14H, I ). Flowers greenish white, regular, staminate flowers smaller than bisexual flowers; hypanthium well developed, short, narrow; calyx bell-shaped, lobes 3-5, subequal; petals 3-5, subequal; stamen number variable, 3-10, haplostemonous or diplostemonous; pollen, exine perforate to reticulate; ovary sessile/stipitate. Fruit stipitate, flat or compressed, indehiscent, papery, leathery or cartilaginous, often with pulpy interior, 1-40-seeded (Fig. 13I ). Seeds elliptic to quadrangular or ovate to circular, compressed to terete.

Chromosome number.

2 n = 28 ( Goldblatt 1981b).

Included species and geographic distribution.

Thirteen species and 1 hybrid taxon. Eastern and central North America to northern Mexico; Bolivia to northern Argentina; China, Tibet, Vietnam, Korea, Japan, Malaysia, Philippines, Azerbaijan (Fig. 17 ). Widespread cultivation of G. triacanthos has greatly expanded its range in North America and obscured its original native area.

Ecology.

Species are generally found in temperate and subtropical woodlands and thickets on sandy and rocky slopes, and lowland wet forest and swamp forest ( Chen et al. 2010d; Poindexter et al. 2022b). Due to widespread cultivation of G. triacanthos in North America its original habitat preferences are unclear.

Etymology.

The genus name commemorates Johann Gottlieb Gleditsch, director of the Berlin Botanical Garden, who died in 1786.

Human uses.

Multiple species of Gleditsia are used by people in different parts of the world ( Gordon 1966; Allen and Allen 1981; Poindexter et al. 2022b). The thornless form of G. triacanthos is widely cultivated as an ornamental and street tree in North America and elsewhere. The sweet fruits are used as a fodder for livestock. The rot resistant wood is used for fence posts, construction and railway ties. The thorns have a variety of historic uses (e.g., as needles and for carding wool). Fruits of some species are rich in saponins and have been used as soap substitutes.

Notes.

Phylogenetic analyses indicate that the genus is monophyletic ( Herendeen et al. 2003b; Schnabel et al. 2003; Manzanilla and Bruneau 2012; LPWG 2013, 2017). The genus was monographed by Gordon (1966). The taxonomy of Chinese species was revised in the Flora of China, which recognised six species in the region ( Chen et al. 2010d). In 2021, G. saxatilis Z.C. Lu, Y.S. Huang & Y. Liu was described from Guangxi, China ( Lu et al. 2021). The species is notable in that it is described to be evergreen. Variability, especially in leaf form, flower structure, and thorn development has resulted in the description of numerous species, subspecies, varieties and forms that are now treated as synonyms under several recognised species, especially G. japonica Miq., G. sinensis Lam. and G. triacanthos .

Taxonomic references.

Allen and Allen (1981); Chen et al. (2010d); Gordon (1966); Poindexter et al. (2022b).

Figures

Figure 13. Gleditsieae, diversity of vegetative morphology and fruits A-C Umtiza listeriana Sim A small tree B branch with pinnately compound leaves and inflorescence C branch with thorn at node D Gymnocladus assamicus Kanjilal ex P. C. Kanjilal branch with bipinnate leaves and inflorescence E Gleditsia japonica Miq., bipinnate leaf with several pinnae replaced by single leaflets, cultivated at the Royal Botanic Gardens, Kew F Gleditsia amorphoides (Griseb.) Taub., branched thorns G Umtiza listeriana dehisced fruits H Gymnocladus dioicus L., fruit I Gleditsia triacanthos L., fruits. Photo credits A-C, G SAplants, Wikimedia Commons (CC-BY-SA 4.0) D B Choudhury E, F GP Lewis H Chicago Botanic Garden (photographer unknown) I A Schnabel.

Figure 14. Gleditsieae, floral diversity A, B Umtiza listeriana Sim A branch with inflorescence of hermaphrodite flowers B close-up of flowers C, D Gymnocladus assamicus Kanjilal ex P. C. Kanjilal C inflorescence of hermaphrodite flowers D dissected hermaphrodite flower E Gymnocladus chinensis Baill., inflorescence, cultivated at the US National Arboretum F Gymnocladus dioicus L., cultivated at Chicago Botanic Garden, upright inflorescence of hermaphrodite flowers G branch with leaves and inflorescence H Gleditsia triacanthos L., inflorescence of staminate flowers I Gleditsia caspica Desf., inflorescence, cultivated at the Royal Botanic Gardens, Kew. Photo credits A, B SAplants, Wikimedia Commons (CC-BY-SA 4.0) C, D Murata E PS Herendeen F, G R Carlson H Royal Botanic Gardens, Kew (photographer unknown) I M Svanderlik.

Figure 17. Distribution of Gleditsia based on quality-controlled digitised herbarium records. See Suppl. material 1 for the source of occurrence data.