Toona
Content
Description
Deciduous or semi-evergreen trees up to 50 m tall, monoecious.
Bark fissured, sometimes flaking irregularly, grey-brown; inner bark pink to red; sapwood cream.
Leaves paripinnate, occasionally imparipinnate.
Inflorescences much-branched pendent thyrses, often exceeding a metre in length.
Flowers 5-merous, unisexual with well- developed vestiges of the opposite sex present, rarely hermaphrodite, small.
Petals 5 (rarely 6), free, longer than the calyx in bud, imbricate (quincuncial), basally adnate to a short pulvinate (cushion-shaped) androgyno- phore (disk); white, cream or pink.
Stamens 5 (rarely 6), free, arising from the andro- gynophore, sometimes alternating with 1–5 filamentous staminodes; anthers in male flowers yellow, dehiscing laterally; antherodes in female flowers often sagittate, brown with abortive pollen.
Ovary 5-locular, each locule with 6–10 ovules, vestigial in male flowers; styles short in female flowers, pistillodes long and slender in male flowers; stylehead discoid with stigmatic papillae, usually 5-rayed.
Fruit a pendulous thinly woody, ellipsoidal or obovoidal, septifragal capsule; valves 5, brown, smooth to ver- rucose, opening from the apex.
Seeds winged either at both ends when attached towards the distal end of the columella, or at one end when attached by the seed-end to the proximal part of the columella; wings membraneous, seeds with residual endosperm.
Distribution
Asia-Tropical, from eastern Pakistan through SE Asia and southern China to eastern Australia present
An Old World genus of 4 or possibly 5 species, extending from eastern Pakistan through SE Asia and southern China to eastern Australia. Three species occur in Malesia.
Taxonomy
The genus is closely allied to the neotropical Cedrela with which it has been repeatedly united and separated from since 1840. Pennington & Styles (1975) proposed clear arguments for the recognition of two distinct genera, with Ce- drela being differentiated from Toona by a columnar androgynophore longer than the ovary, and seedlings having entire leaflets. The genera are also distinguishable by various other characters, with chromosomal evidence suggesting different evolution- ary histories. Species of the genus Toona are extremely variable, especially in their vegetative morphology; average parameters have not been included in all of the spe- cies descriptions.
Monographic study of this genus has demonstrated that it is composed of very few species, and that phenotypic plasticity and genetic variation are responsible for much of the taxonomic complexity reflected in the literature. The species exhibit a phenomenal range of morphological variation, both within and between trees of the same population, and many of the features used by earlier workers to define their taxa, have proved to be only slight morphological variants. Such vegetative characters include leaf and leaflet size; leaflet and leaflet-margin shape; indumentum type and hair density. In particular, the velutinous pubescence, on which a number of Toona taxa have been based, occurs throughout the genus with the exception of T. sinensis, both inter- and infra-specifi- cally, and even between seedlings of the same population.
Though the monographic revision of these species at the specific level is nearing completion, the floral and vegetative variation observed in the species could represent extreme ranges of polymorphic species, or be genetically stable and eco-geographically correlated, and therefore be given formal recognition. The taxonomy at the infraspecific level is therefore complex and still under review; future conclusions could necessitate some changes in the taxonomy of this genus.
Monographic study of this genus has demonstrated that it is composed of very few species, and that phenotypic plasticity and genetic variation are responsible for much of the taxonomic complexity reflected in the literature. The species exhibit a phenomenal range of morphological variation, both within and between trees of the same population, and many of the features used by earlier workers to define their taxa, have proved to be only slight morphological variants. Such vegetative characters include leaf and leaflet size; leaflet and leaflet-margin shape; indumentum type and hair density. In particular, the velutinous pubescence, on which a number of Toona taxa have been based, occurs throughout the genus with the exception of T. sinensis, both inter- and infra-specifi- cally, and even between seedlings of the same population.
Though the monographic revision of these species at the specific level is nearing completion, the floral and vegetative variation observed in the species could represent extreme ranges of polymorphic species, or be genetically stable and eco-geographically correlated, and therefore be given formal recognition. The taxonomy at the infraspecific level is therefore complex and still under review; future conclusions could necessitate some changes in the taxonomy of this genus.
Uses
The timbers of Toona spp. are highly prized but generally scarce. Toona ciliata was the most important native timber in Australia but is now largely cut out; the Malesian species seem to be undergoing a similar fate. Extracts from the bark, heart- wood and leaves apparently have insecticidal qualities.
Citation
Burkill 1930 – In: Gard. Bull. Str. Settl.: 120
Pellegrin 1911 – In: Fl. Indo-Chine: 792
Burkill 1935: Dict. Econ. Pl. Malay Penins.: 499
Bahadur 1988: Monogr. Toona: 1–251.
Harms 1896 – In: Engl. & Prantl, Nat. Pflanzenfam. 3, 4: 269
Symington 1935 – In: Malay For.: 119.
T.D. Penn. & Styles 1975 – In: Blumea: 512
Harms 1940: p. 44. – In: Engl. & Prantl, Nat. Pflanzenfam., ed. 2, 19bl: t. 2.