Rosidae: Rosales. The Rosaceae are trees, shrubs and herbs comprising about 100 genera and 3,000 species. Most species have alternate leaves and stipules. These may be adnate to the petiole. You have likely heard the saying, "a rose is a rose is a rose," suggesting that when you've seen one, you've seen them all. The family does tend to have somewhat monotonous actinomorphic flowers, commonly with 5-parted perianth and numerous stamens. However, closer inspection reveals that the gynoecium varies tremendously among different species of the family. In the subfamily Rosoideae many apocarpous pistils mature into achenes while in the Prunoideae a single monocarpellate pistil matures into a drupe. In subfamily Spiraeoideae the gynoecium consists of two or more apocarpous pistils that mature into follicles. In all of these cases the ovary is superior and there is commonly some development of a perigynous zone. However, in a fourth subfamily, Maloideae, the ovary is compound and inferior, and an epigynous zone may occur.
Each "thumbnail" image below is linked to a larger photograph.
|Subfamily Rosoideae, Rosa californica, wild rose.|
|Subfamily Rosoideae, Potentilla sp. Note five-parted calyx, 5 distinct petals, numerous distinct stamens on a short perigynous zone, and numerous distinct pistils maturing into achenes.|
|Subfamily Rosoideae, Fragaria sp., strawberry. In the longitudinal section of the flower note the perigynous zone bearing calyx, distinct petals, and numerous distinct stamens. Note also the elongated receptacle bearing numerous distinct pistils that develop into achenes. As fruiting ensues, the individual achenes, which do not change much in size, become spatially isolated on the surface of the greatly enlarged receptacle (aggregate accessory fruit).|
|Subfamily Rosoideae, Rubus sp., raspberry. Note the numerous stamens and the aggregate fruit resulting from coalescence of the numerous pistils.|
|Subfamily Rosoideae, Rubus pedatus. This species has a very low number of pistils.|
|Subfamily Prunoideae, Prunus sp. Longitudinal section of flower. Note well developed perigynous zone bearing sepals, petals, and numerous stamens. Note also the single simple pistil that matures into a drupe.|
|Subfamily Spiraeoideae, Luetkea pectinata, partridge feet. Note the 5 pistils which mature into follicles.|
|Subfamily Spiraeoideae, Spiraea sp.|
|Subfamily Maloideae, Chaenomeles. Longitudinal section of flower. Note the compound inferior ovary, the 5-branched style, and the epigynous zone that bears the sepals, petals, and numerous stamens.|
|Subfamily Maloideae, Eriobotrya japonica, loquat. Small tree from China and S. Japan with edible fruits that are eaten raw or cooked or made into jelly.|
|Subfamily Maloideae, Osteomeles anthyllidifolia, ulei. Note the typical "rose" flowers and the apple-like fruits from inferior compound ovaries (literally "bone apples" from the generic name).|
|Subfamily Maloideae, Raphiolepis umbellata, oriental hawthorn.|
|Subfamily Maloideae, Pyracantha angustifolia, firethorn.|
Flowering Plant Family Access Page