from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The ringlike, cup-shaped, or tubular structure of a flower on which the sepals, petals, and stamens are borne, as in the flowers of the rose or cherry.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The bowl-shaped part of a flower on which the sepals, petals, and stamens are borne
from the GNU version of the Collaborative International Dictionary of English
- n. A fruit consisting in large part of a receptacle, enlarged below the calyx, as in the Calycanthus, the rose hip, and the pear.
from The Century Dictionary and Cyclopedia
- n. In botany, an enlargement or other development of the torus under the calyx. Gray.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. the cuplike or ringlike or tubular structure of a flower which bears the sepals and stamens and calyx (as in Rosaceae)
The magnificent trumpet that thrusts out of the flower and announces the arrival of spring is a freak of nature, an elongated portion of the flower called the hypanthium.
The calyx and corolla are fused to form a floral tube (also called a hypanthium) that is cylindrical (4-6 mm long), greenish, and 8-12 nerved.
It's only revealed in certain flowers after pollination – when you eat an apple, for instance, you are biting into a thick, fleshy hypanthium.
But in the daffodil, the hypanthium enlongates into the trumpet, a unique flower organ.
I want to stop smelling the basal stipules, pinnate leaflets, hypanthium and achenes.
Mr. Bentham, who has recently reviewed the evidence as to the nature of the calyx-tube in his paper on _Myrtaceæ_,  still holds to the notion that the "calyx-tube" or "hypanthium" is formed from the concretion of the basal portions of the sepals.
The structure now is regarded as a hollowed receptacle or stem (hypanthium), with the pistil inside, the petals and stamens on its rim.
Technically, it is not a fruit but a false fruit, meaning the fleshy part is derived not from the plant's ovaries (achenes) but from the peg at the bottom of the bowl-shaped hypanthium that holds the ovaries.
(achenes) but from the peg at the bottom of the bowl-shaped hypanthium that holds the ovaries.