ROSACEAE (Rose Family)
Plants annual or
more commonly perennial, herbs, shrubs, or trees, sometimes armed with thorns
or prickles. Leaves alternate (opposite in Rhodotypos and sometimes in Geum)
or all basal. Stipules present, herbaceous, scalelike, or spinescent. Leaf
blades simple or compound, the margins usually toothed or lobed, the teeth
often with small glandular points. Inflorescences axillary and/or terminal
clusters, racemes, spikes, panicles, or umbels, rarely solitary flowers.
Flowers usually perfect (except in the mostly dioecious Aruncus),
actinomorphic (slightly zygomorphic in Gillenia), perigynous or
epigynous, often with a noticeable hypanthium (floral cup or disc), but
sometimes appearing nearly hypogynous. Sepals 4 or 5, free, sometimes appearing
fused basally in species with a well-developed hypanthium, often persistent at
fruiting. Petals 4 or 5 (to numerous in some horticultural variants), rarely
absent, free. Stamens (1–)10 to numerous, often in multiples of 5, usually
free, the anthers with 2 locules, dehiscing by longitudinal slits. Pistils 1 to
many per flower, each apparently with 1–5 carpels. Ovary superior or inferior,
with 1 or less commonly 2 locules, each with 1 to few ovules. Styles 1–5, free
or fused toward the base, each with 1 stigma, this minute to disc-shaped and
terminal or linear and lateral toward the style tip. Fruits diverse. About 100
genera, about 3,000 species, worldwide.
The Rosaceae are
an extremely diverse group morphologically, and the characters that hold
members of the family together may not be immediately obvious to botany
students. A complex classification exists involving 3 or more subfamilies with
up to 13 tribes, but many details of generic relationships remain
controversial. The most recognizable traditionally accepted subfamilies are:
Spiraeoideae Arn. (including Aruncus, Gillenia, Physocarpus, and Spiraea),
with flowers containing 2 or more pistils that ripen into follicles; Amygdaloideae
Arn. (in Missouri, including only Prunus), with the flowers having only
1 pistil ripening into a drupe; and Maloideae C. Weber (including Amelanchier,
Aronia, Chaenomeles, Crataegus, Malus, Pyracantha, and Pyrus), with
inferior ovaries ripening into a specialized fruit type known as a pome, which
is a fleshy fruit with a core containing seeds surrounded by the hardened or
papery, modified inner ovary walls. Most recently, the Amygdaloideae and
Maloideae have been suggested to represent merely specialized tribes within the
subfamily Spiraeoideae (Potter et al., 2007). The other subfamily, Rosoideae,
with indehiscent fruits of various kinds, consists of genera with a diversity
of habits, flower types, and other features.
Various members
of the family have great economic value as fruit plants, ornamentals,
ingredients in cosmetics and soaps, and minor timber trees. A number of species
are used medicinally and as sources of vitamins.