16. Cucumis Linnaeus, Sp. Pl. 2: 1011. 1753; Gen. Pl. ed. 5, 442. 1754.
Melon, cucumber [Latin name for cucumber] Melon, cucumber [Latin name for cucumber]
Cucumella Chiovenda; Dicoelospermum C. B. Clarke; Melo Miller; Mukia Arnott; Myrmecosicyos C. Jeffrey; Oreosyce Hooker f.
Plants annual [perennial], usually monoecious, rarely dioecious (C. anguria) or andromonoecious (C. melo), procumbent, trailing, or climbing; stems <annual>, hispid to hirsute; roots woody or thin [rarely tuberous]; tendrils usually unbranched, rarely unbranched and 2-branched or absent. Leaves: blade ovate, palmately 3–6[–7]-lobed or unlobed, lobes triangular or elliptic, oblong, ovate, obovate, or spatulate, margins serrate or entire, surfaces eglandular. Inflorescences: staminate flowers solitary or 2–10(–18) in axillary racemes, fascicles, or panicles; pistillate flowers usually solitary, rarely 2 or 3 in fascicles, from different axils than staminate, <peduncles straight in fruit>; bracts absent [rarely present]. Flowers <unisexual (rarely gynecandrous in C. metuliferus)>; hypanthium infundibular to campanulate, <2–10 mm>; sepals (4–)5, <straight>, linear to oblong or narrowly to broadly triangular; petals 5, distinct or basally connate, yellow, elliptic to ovate or obovate, 2–25[–37] mm, glabrous or pubescent, corolla campanulate to infundibular (constricted distally into a neck). Staminate flowers: stamens 3; filaments inserted near hypanthium base, distinct; thecae distinct, oblong, replicate (usually 2-folded) [straight to arcuate], connective broadened; pistillodes absent. Pistillate flowers: ovary 3–5-locular, ovoid to ellipsoid; ovules 15–150 per locule; style 1, short-columnar; stigmas 1, sublobate to 3-lobed, lobes sometimes with 1–9 fingerlike projections on margins; staminodes present or rarely absent. Fruits pepos, mono- or bicolor, green to yellow, orange, or tan [white, brown, purple] with light or dark green, white, yellow, brown, or orange [purple] longitudinal stripes, usually ellipsoid, globose, or cylindric, rarely obovoid [ovoid, rarely spindle-shaped], smooth, <glabrous, surfaces densely echinate, or aculeate to muricate, sometimes netted, warty, scaly, or ridged>, indehiscent. Seeds 50–500, ellipsoid to ovoid, compressed, not arillate, margins not differentiated, surface smooth. x = 12.
Species ca. 55 (6 in the flora): introduced; Asia (China, India, Indonesia, Malaysia), Africa, Atlantic Islands (Cape Verde Islands), Indian Ocean Islands (Aldabra, Madagascar, Seychelles), Pacific Islands (Philippines), Australia; also introduced nearly worldwide.
Two Cucumis species are major commercial vegetable crops––C. melo, the melons (cantaloupes, honeydew, muskmelons, sugar melon, winter melon) and C. sativus, the garden cucumber. Cucumis anguria (the West Indian gherkin) and C. metuliferus (the kiwano) also are used commercially.
Most Cucumis plants in the flora area are escapes from gardens, trash dumps, or picnic discards and do not persist long outside cultivation. The dudaim melon (C. melo), paddy melon (C. myriocarpus), and a few others possibly have the potential to become aggressively invasive.
C. Jeffrey (1980b) recognized Cucumis subg. Cucumis (comprising two species, C. sativus and the closely similar C. hystrix Chakravarty) and subg. Melo (Miller) C. Jeffrey. Infrageneric classification has been modified by L. W. D. van Raamsdonk et al. (1989) and J. H. Kirkbride (1993), and based on insights from molecular data, H. Schaefer (2007) divided the genus into two subgenera, subg. Cucumis (50 species in five sections) and subg. Humifructus H. Schaefer (two species).
C. Jeffrey (1990) circumscribed the subtribe Cucumerinae (tribe Melothriae) to include Cucumis and five smaller genera––Cucumella, Dicoelospermum, Mukia, Myrmecosicyos, and Oreosyce. Molecular studies (A. G. Ghebretinsae et al. 2007; H. Schaefer 2007) indicate that Cucumis is paraphyletic without the 19 species of these five genera, and Schaefer formally broadened Cucumis to include them.
An Asian origin has been demonstrated for both Cucumis melo and C. sativus by P. Sebastian et al. (2010), using data from plastid and nuclear DNA. The wild progenitor of C. melo occurs in India and its sister species is C. picrocarpus F. Mueller from Australia. The closest relative of C. sativus is C. hystrix Chakravarty from the eastern Himalayas. The Asian/Australian Cucumis clade comprises at least 25 species.
The sister genus to Cucumis is Muellerargia Cogniaux, with one species in Madagascar (M. jeffreyana Keraudren) and one in Indonesia and Australia (M. timorensis Cogniaux). Both are in African/Asian clades that include the genera Coccinia Wight & Arnott, Neoachmandra de Wilde & Duyfjes, Peponium Engler, and Zehneria Endlicher (S. S. Renner and H. Schaefer 2008).
Cucumis sativus (subg. Cucumis) is the only species of the genus reported to have a chromosome number of 2n = 14; the only other species of subg. Cucumis (fide J. H. Kirkbride 1993), C. hystrix, has been reported to have a number of 2n = 24 (Chen J. F. et al. 1997). All Dysploid numbers of 2n = 20 and 2n = 22 have been reported from C. melo, which otherwise has 2n = 24. The chromosome number of Muellerargia has not been reported.
Most of the 52 species of Cucumis in the sense of Jeffrey are monoecious perennials, and key difference in Cucumis, and the mode of fruit opening also are much more evolutionarily labile than formerly thought (for details see S. S. Renner et al. 2007).
The monograph by J. H. Kirkbride (1993) has been a primary source in preparing this treatment.
SELECTED REFERENCES Chung, S. M., J. E. Staub, and J. F. Chen. 2006. Molecular phylogeny of Cucumis species as revealed by consensus chloroplast SSR marker length and sequence variation. Genome 49: 219–229. Ghebretinsae, A. G., M. Thulin, and J. C. Barber. 2007. Relationships of cucumbers and melons unraveled: Molecular phylogenetics of Cucumis and related genera (Benincaseae, Cucurbitaceae). Amer. J. Bot. 94: 1256–1266. Kirkbride, J. H. 1993. Biosystematic Monograph of the Genus Cucumis (Cucurbitaceae): Botanical Identification of Cucumbers and Melons. Boone, N.C. Naudin, C. V. 1859. Essais d’une monographie des espèces et des variétés du genre Cucumis. Ann. Sci. Nat., Bot., sér. 4, 11: 5–87. Raamsdonk, L. W. D. van, A. P. M. Nijs, and M. C. Jongerius. 1989. Meiotic analyses of Cucumis hybrids and an evolutionary evaluation of the genus Cucumis. Pl. Syst. Evol. 163: 133–146. Renner, S. S. and H. Schaefer. 2008. Phylogenetics of Cucumis (Cucurbitaceae) as understood in 2008. In: M. Pitrat, ed. 2008. Cucurbitaceae 2008: Proceedings of the IXth EUCARPIA meeting on Genetics and Breeding of Cucurbitaceae, Avignon (France), May 21–24th, 2008. Avignon. Pp. 53–58. Renner, S. S., H. Schaefer, and A. Kocyan. 2007. Phylogenetics of Cucumis (Cucurbitaceae): Cucumber (C. sativus) belongs in an Asian/Australian clade far from melon (C. melo). B. M. C. Evol. Biol. 7: 58. Schaefer, H. 2007. Cucumis (Cucurbitaceae) must include Cucumella, Dicoelospermum, Mukia, Myrmecosicyos, and Oreosyce: A recircumscription based on nuclear and plastid DNA data. Blumea 52: 165–177. Sebastian, P. et al. 2010. Cucumber (Cucumis sativus) and melon (C. melo) have numerous wild relatives in Asia and Australia, and the sister species of melon is from Australia. Proc. Natl. Acad. Sci. U.S.A. 107: 14269–14273.