Eulophia streptopetala flower

Contrast between yellow petals and brown sepals is the highlight of this Eulophia streptopetala flower. There are three of each, as the lip is really a petal, the third member of the inner whorl of segments of a typical orchid flower perianth; or all six of them tepals as in lilies.

But orchids differ from lilies, their monocot relatives, in being laterally symmetric (zygomorphic), not radially symmetric (actinomorphic). Orchid lips assume unique shapes, colours and sizes, often putting them so far apart from the pair of lateral petals that their common structural origin is ignored. The lip in picture has two brown lateral lobes.

The somewhat flattened, pale cylinder that is the column protrudes forward. The mentum, a chin-like projection formed by the sepal bases and the base of the column is broad, similar in length to the column in this Eulophia (Liltved and Johnson, 2012; Wikipedia).