A rostellum is a small beak-like projection, especially the small projection on the stigma of an orchid.
Rostellums are a part of a flower, especially an orchid, and are important for reproduction.
Examples:
The rostellum helps the orchid make seeds.
The bee lands on the rostellum of the orchid.
The rostellum is a small part of the flower.
The rostellum looks like a tiny bird beak.
The rostellum is like a little nose on the flower.
The rostellum is very important for the orchid to have babies.