Key to sections and species of Ypsilopus Summerh.
1a | Leaves spread along the stem, flower spur at least 7.5 cm long, column at least 5 mm long | sect. Barombiella:2 |
1b | Leaves arranged in a fan, flower spur less than 5 cm long, column less than 2 mm | sect. Ypsilopus:3 |
2a | Column longer than 2 cm | Ypsilopus schliebenii |
2b | Column less than 2 cm long | Ypsilopus amaniensis |
3a | Inflorescence 1-2-flowered | Ypsilopus viridiflorus |
3b | Inflorescence 3- to many-flowered | 4 |
4a | Plant pendent | Ypsilopus longifolius |
4b | Plant erect | 5 |
5a | Leaves shorter than 7 cm, flowers subcampanulate | Ypsilopus leedalii |
5b | Leaves longer than 10 cm, flowers not subcampanulate | 6 |
6a | Lip obscurely 3-lobed, sub-rhombic to ovate, acute | Ypsilopus erectus |
6b | Lip clearly 3-lobed with spreading side lobes and an acute, triangular median lobe | 7 |
7a | Spur more than 3 cm long, flowers bright yellow | Ypsilopus citrinus |
7b | Spur less than 3 cm long, often much shorter, flowers white fading to orange-yellow | 8 |
8a | Leaves spotted dark green on a paler background in both fresh and dried material | Ypsilopus tanneri |
8b | Leaves unspotted | 9 |
9a | Spur inflated toward the apex | Ypsilopus sarcodanthus |
9b | Spur slender, not inflated | 10 |
10a | Flowers with tepals 5-7.5 mm long, side lobes erose or bifid | Ypsilopus tricuspis |
10b | Flowers with tepals 8-12 mm long, side lobes slender and acute | Ypsilopus furcistipes |
Excluded species
Ypsilopus liae Delep. & J.-P.Lebel, as it lacks the characteristic Y-shaped stipes of Ypsilopus, and had been described before as Diaphananthe arbonnieri Geerinck, is actually a species of Rhipidoglossum as firstly pointed out by Fischer & al. (2011).
References:
Molecular phylogeny and taxonomic synopsis of the angraecoid genus Ypsilopus (Orchidaceae, Vandeae) TAXON 68 (3) June 2019: 455–470; WCSP (2020). 'World Checklist of Selected Plant Families. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; http://wcsp.science.kew.org/ Retrieved 31 October 2020.'