Answers are grounded in this paper and cite their sources.
Anatomically preserved stems from the Late Permian (250 to 270 million years ago) of China have been discovered that contain vessels. The stems possess several features commonly found in vines, including tendril-like appendages, and are associated with large leaves assignable to the Gigantopteridales, an enigmatic group of Permian plants. The individual vessel elements contain foraminate perforation plates in their end walls and are anatomically similar to the conducting elements of modern gnetophytes and of some extant flowering plants.
No takes yet. Share an insight, caveat, or question.
Li et al. (1996) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: