1a. Stem suberect, climbing or scandent, up to 300 cm; inflorescence axillary......................................................................................2
1b. Stem erect, up to 10 cm; inflorescence terminal................................................................................................... S. cucphuongense
2a. Suberect or ascending herbs...................................................................................................................................... S. puluongense
2b. Climbing or scandent herbs................................................................................................................................................................3
3a. Leaf blade lanceolate or ovate-lanceolate; ovary glabrous......................................................................................... S. longifolium
3b. Leaf blade broadly oblong or broadly lanceolate; ovary densely hirsute........................................................................... S. elegans