Rosaceae: Prunoideae - drupes
Drupes are fleshy fruits in which the inner part of the ovary wall becomes a hard and woody pyrene, while the outer part remains soft and may be invested with sugars and water, or with lipids. These nutrients may serve as food rewards for potential animal dispersal vectors, i.e. they may represent adaptations for endozoochory. Not all drupes are fleshy and associated with endozoochory; coconuts are just as much drupes as dates are.
Most members of Rosaceae subfamily Prunoideae produce drupes that develop
from the single pistil of a perigynous flower, as shown below. An exception
is the genus Oemleria (osoberry), from the Pacific northwest, in which
up to five pistils are found within the hypanthium. The largest genus in the
subfamily is Prunus L. (cherries, plums, peaches, apricots, almonds).
The "pome" fruits that develop from the hypanthial
ovaries of some members of subfamily Maloideae are technically also (polypyrenous)
Photo: M. Ferguson © 1998 Royal Ontario Museum
Prunus nigra (Canada plum)
Photo: R. Presgrave © 2000 Royal Ontario Museum (TRT1824)
Prunus virginiana (chokecherry) - racemes of drupes, each of which develops from the single pistil found at the center of the hypanthial cup (diagram above).
Flower and fruit illustrations from Strasburger et al. (1898) A textbook of botany; compare Judd et al. Fig. 8.74).
Mulligan, G. A. & D. B. Munro, 1981. The Biology of Canadian Weeds 51. Prunus virginiana L. and P. serotina Ehrh. Can. J. Plant Sci. 61: 977-992. [includes key to species native to Canada]
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