The genus Eulophia in Madagascar
The orchid genus Eulophia consists of about 200 species which are very widely distributed in Africa, and also occur in Central America, India and South-East Asia.
The earliest descriptions of members of this genus were based on plants from South Africa. They were published in the late 18th century by the younger Linnaeus and were placed in the genus Satyrium. The generic name was published by Robert Brown in 1821, and in the same article the generic name Eulophus was suggested for an allied series of species, without a description or any formal transfer of epithets. This name was validly published in the form Eulophia two years later by Lindley.
Preliminary studies in the genus Eulophia showed that while some groups could be distinguished from one another without difficulty, others showed complex intergrading series, with or without higher frequencies of one or more forms. Complex variation patterns of this sort have been recorded before in the genus Eulophia. chiefly among the tropical African team (e.g. de Wildeman 1919, Summerhayes 1933, 1958).
The present work was undertaken to provide a much-needed taxonomic revision of the Madagascar members of the genus Eulophia R.Br. (Orchidaceae).
The genus is particularly well represented in South Africa where its distribution is centered in the Eastern Cape, KwaZulu-Natal, Mpumalanga and the Northern Province. While many Eulophias are endemic to this country, the distribution range of several species found here extends into Central and West Africa.
Key to the genus Eulophia in Madagascar

1a Tubercule solitaire, liypogé, conique, dressé, couvert de petites écailles charnues, n’émettant de racines qu’à, la base;
saprophyte sans chlorophylle, aphylle
section Saprolophia
2a Tubercules 3-6, hypogés, disposés en série linéaire horizontale, charnus, aplatis, plus ou moins anguleux, élargis de la base
au sommet, le plus nouveau inséré par sa base étroite sur le sommet large du précédent, lisses mais avec d’étroites cicatrices
foliaires, portant des racines sur leur face inférieure seulement; plantes à feuilles vertes, caduques au fur et à mesure du
renflement en tubercule du bourgeon qui les porte
section Lissolophia
3a Pseudobulbes épigés ou semi-épigés, dressés, plus ou moins verts ou fibreux, disposés en série linéaire, coniques ou
fusiformes, ne portant de racine qu’à leur base; feuilles vertes, caduques seulement: chez quelques espèces epiphytes,
persistantes chez toutes les autres 
section Eueulophia

Eulophia species without a key in Madagascar

Eulophia angornensis (Rchb.f.) P.J.Cribb, Comoros.
Eulophia borbonica Bosser, Réunion (Cirque de Mafate).
Eulophia clitellifera (Rchb.f.) Bolus Trop. & S. Africa, Madagascar. 
Eulophia cucullata (Afzel. ex Sw.) Steud Trop. & S. Africa, Comoros, Madagascar. 
Eulophia ephippium (Rchb.f.) Butzin  Madagascar. 
Eulophia filifolia Bosser & Morat S. Madagascar. 
Eulophia hians Spreng., Ethiopia to S. Africa, Madagascar, SW. Arabian Pen. 
Eulophia mangenotiana Bosser & Veyret N. & C. Madagascar. 
Eulophia pulchra (Thouars) Lindl. Tanzania to Mozambique and W. Pacific. 

World Checklist of Monocotyledons. The Board of Trustees of the Royal Botanic Gardens, Kew. Published on the Internet; accessed 25/08/2019