SIMAROUBACEAE (Quassia Family)
Plants shrubs or
trees, functionally dioecious (but sometimes incompletely so or the flowers
sometimes appearing perfect; monoecious elsewhere), often colonial from root
sprouts, usually with internal secretory canals, but these not visible
externally, the tissues sometimes with a strong odor when plant parts are
bruised or crushed. Stems or trunks 1 to several from the base, erect or
ascending, branched or less commonly unbranched, unarmed. Leaves alternate,
petiolate. Stipules absent (occasionally represented by a pair of minute glands
in Ailanthus). Leaf blades simple and unlobed or pinnately compound, the
leaflets then opposite, sessile, unlobed. Inflorescences terminal,
many-branched panicles or axillary, dense catkins. Flowers usually imperfect
(but sometimes appearing perfect by well-developed appearance of staminodes
and/or nonfunctional pistils), hypogynous, actinomorphic, sessile or stalked.
Calyces absent or of (3)4 or 5(–8) sepals, these sometimes minute, free or
fused at their bases, usually overlapping in bud, ascending or spreading, often
persistent at fruiting. Corollas absent or of 5 petals, these free, not
overlapping in bud, spreading to curved or curled downward. Staminate flowers
with (3)8–12(–15) stamens (individual flowers difficult to distinguish in Leitneria),
the filaments distinct, sometimes hairy or with small appendages near the base,
the anthers attached at or above the base, yellow; pistillate flowers with
staminodes absent (Leitneria) or 3–5 and stamenlike in appearance (Ailanthus).
Nectar disc sometimes present, often lobed. Pistil(s) 1–5 per flower, of 2–5
carpels, these fused, at least below the midpoint; absent or rudimentary in
staminate flowers (well-developed externally elsewhere). Ovaries superior,
1–5-locular, the placentation lateral (when 1-locular) or axile (when
2–5-locular). Style 1 per flower, sometimes with twisted, longitudinal lines
equal to the carpel number, the stigma either a receptive region near the
grooved style tip or capitate and 2–5-lobed. Ovule 1 per carpel. Fruits drupes
or technically schizocarps, but then appearing as small clusters of samaras.
Seeds various in size and appearance. Thirteen genera, about 95 species, North
America to South America, Asia to Australia.
The familial
circumscription of Simaroubaceae has changed greatly since the application of
molecular techniques to the study of phylogeny in the family and its relatives.
Traditionally, the family was thought to comprise about 30 genera and 200
species that were most diverse in the tropics of both the Old and New Worlds,
but affinities of the family within the order Sapindales were poorly understood
(Channell and Wood, 1962). Sequence analyses of the rbcL marker
(Fernando and Quinn, 1995; Fernando et al., 1995; Gadek et al., 1996) disclosed
that several genera should be transferred to the closely related family
Rutaceae and that others were even more distantly related and should be
classified into segregate families, some of them in other orders. Perhaps most
surprisingly, these studies indicated strongly that the genus Leitneria,
previously treated in its own taxonomically isolated family (Cronquist, 1981,
1991), should be included in the Simaroubaceae in the strict sense. This
reclassification results in a family that is morphologically very diverse, but
whose genera share a suite of anatomical and phytochemical features.
Members of the
family have relatively minor economic importance. Some species are harvested
for timber in Asia and a number of species have been used medicinally,
particularly for their inner bark and seeds, which are rich in triterpenoid
lactones (thus bitter, astringent). A few species are cultivated shade trees or
specimen plants.