Gnetophyta consists of three genera, "Ephedra", "Gnetum" and "Welwitschia". Cronquist considered the vessels of "Gnetum" to be convergent with those of angiosperms. Specifically, this event has been documented in both "Ephedra" and "Gnetum", a subset of Gnetophytes. Some perennials such as "melinjo" ("Gnetum gnemon") produce leaves consistently. Though bearing leaves, the genus "Gnetum" are gymnosperms, related to pine and other conifers. Pinostilbene is a stilbenoid found in "Gnetum venosum" and in the bark of "Pinus sibirica". Two meninjau trees ("Gnetum gnemon") stand near the visitor center. It is present in the heartwood of "Pinaceae" and also found in "Gnetum cleistostachyum". In "Gnetum gnemon", numerous free egg nuclei exist in female cytoplasm inside the female gametophyte. Gnetum macrostachyum is a species of vine gymnosperm, native to tropical Asia. "Gnetum africanum" is traditionally a wild vine and is considered to be a wild vegetable.