Echinocystis Torr. & A. Gray
Echinocystis Torr. & A. Gray, Fl. N. Amer. 1: 542. 1840 (nom. cons.).
Type: Echinocystis lobata (Michx.) Torr. & A. Gray; basionym: Sicyos lobatus Michx., T.F. Lucy 3452 (US), neotype designated by Stocking, Madroño 13: 86. 1955.
Pseudoechinopepon (Cogn.) Cockerell, Bot. Gaz. 24: 378. 1897.
Annual climbing herb with up to several meters long shoots and monoecious sex system. The leaves are simple, petiolate, with 5-lobed blade. The tendrils are tri- to pentafid. The flowers are small, the male flowers in racemes, the female flowers solitary (rarely pairs), coaxillary with the male raceme. The receptacle-tube is flat with six sepals. The corolla is rotate with six white petals. The three stamens are inserted near the center of the tube on very short filaments. The triplicate thecae contain penta-colporate, perforate, medium-sized pollen (polar axis c. 54 µm, equatorial axis c. 60 µm (Khunwasi 1998)). The ovary is globose, echinate with two placentae and very short style with capitate stigma. The fruit is an ovoid, fleshy pepo, echinate with slender spines, apically dehiscent. The four seeds are compressed with pale brown testa. The chromosome number is n = 16 (Samuel et al. 1995, Gervais et al. 1999).
The only species, Echinocystis lobata grows in thickets, along roadsides and in other disturbed areas in Eastern North America.
Echinocystis is sister genus to Marah, from which it split about 15 million years ago (Schaefer et al., 2009; Schaefer & Renner 2011).
Echinocystis lobata (Michx.) Torr. & A. Gray, Fl. N. Amer. 1: 542. 1840.
Gervais, C., Trahan, R., Gagnon, J. 1999. IOPB chromosome data 14. Newslett. Int. Org. Plant Biosyst. 30: 10-15.
Khunwasi, C. 1998. Palynology of the Cucurbitaceae. Doctoral Dissertation Naturwiss. Fak., University of Innsbruck.
Samuel, R., Balasubramaniam, S., Morawetz, W. 1995. The karyology of some cultivated Cucurbitaceae of Sri Lanka. Ceylon J. Sci., Biol. Sci. 24: 17-22.
Schaefer, H. and S.S. Renner. 2011. Phylogenetic relationships in the order Cucurbitales and a new classification of the gourd family (Cucurbitaceae). Taxon 60: 122-138.
Schaefer, H., Heibl, C., and S.S. Renner. 2009. Gourds afloat: a dated phylogeny reveals an Asian origin of the gourd family (Cucurbitaceae) and numerous oversea dispersal events. Proceedings of the Royal Society B 276: 843-851.
Stocking, K. M. 1955. Some considerations of the genera Echinocystis and Echinopepon in the United States and northern Mexico. Madroño 13: 84-100.