Icacinaceae

Primary tabs

Icacinaceae

Description

Trees, or whether or not climbing shrubs, or lianas. HEINTZELMANN & HOWARD () distinguish ten hair types that occur in floral parts or on leaves and young twigs of Icacinaceae. Noteworthy are the two-armed or Malpighiaceous hairs in Nothapodytes and some genera from outside Malesia. This hair type intergrades with the so-called Icacinaceous hair with one much reduced and one well developed arm occurring in a majority of the genera. Rhyticaryum has clustered hairs; Platea stellate-peltate hairs (called 'scales' in the taxonomic part) (see also ).

Stomata are very imperfectly known in Icacinaceae. Both anomocytic and paracytic stomata have been recorded in literature, but actinocytic (Merrilliodendron) and anisocytic (Medusanthera and Stemonurus) types also occur.

The vascularization of the petiole and midrib would also merit further investigation. Species of Apodytes, Citronella, Medusanthera, Phytocrene, and Stemonurus have central strands with or without latero-dorsal bundles, but the range in the whole family must be much greater since Pennantia shows a very complex pattern (cf. ).

Crystals occur as druses, solitary rhomboids and crystal sand in various combinations (cf. ).

The fine translucent dots of the leaves of Merrilliodendron are caused by large intercellular spaces in the spongy tissue of the mesophyll.

Domatia have been recorded for several Icacinaceous genera but are absent from all Malesian species. — P. BAAS.
Leaves spirally arranged, rarely opposite, simple, entire or lobed (in Mal. never crenate or serrate), penni-or palmatinerved, exstipulate. Inflorescences mostly axillary, sometimes terminal, rarely extra-axillary, or from old wood, in spikes or spike-like racemes, or often in cymes, both spikes and cymes not rarely collected to panicles or heads, very rarely reduced to few-flowered fascicles or to a solitary flower. Flowers bi- or unisexual, in the latter case at least functionally so, i.e. the plants dioecious, actinomorphic, (4-)5(-6)-, by reduction rarely in part 3-merous, cyclic (with sepals or calyx lobes and petals) or rarely spiral (with petals only in Pyrenacantha, or without petals in the ♀ flowers of Platea and some spp. of Iodes and Gomphandra). Sepals 4-6, free or mostly connate below to various degree to a 4-6-lobed calyx, the lobes imbricate or valvate, generally persistent. Petals 4-6, free or connate below to various degree, sometimes to a tube, the lobes valvate, very rarely subimbricate, tip inflexed, mostly caducous, sometimes persistent. Stamens as many as sepals or petals, episepalous, inserted basally or sometimes in the upper part of the tube; Ovary free, 1-celled (in Pseudobotrys, Gonocaryum and Citronella 2-celled with an empty tube-like unilateral cell) (in Mal.); Seed 1, exarillate, generally with abundant endosperm, which rarely is ruminate;

Distribution

Africa: present Asia: present Asia-Temperate:, Hainan (Hainanpresent) Asia-Tropical:, Assam (Assampresent); East Himalaya (Sikkimpresent); New Guineapresent; Thailand (Thailandpresent) Australasia:, Queensland (Queenslandpresent) Bengal: present Burma: present Central Chile: present Ceylon: present E. Australia: present Madagascar: present Melanesia: present Micronesia: present N. Argentina: present NE. Australia: present New Britain: present New Caledonia: present New Hebrides: present New Zealand: present Norfolk I: present Pacific:, Fiji (Fijipresent); Samoa (Samoapresent); Tonga (Tongapresent) S. America: present S. Japan: present S. and SE. Asia: present SE. Asia: present SE. New Guinea: present SW. India: present Solomon Is: present Southeast Asia: present Southern America:, Argentina Northeast (Formosapresent); Bolivia (Boliviapresent); Costa Rica (Costa Ricapresent); Paraguay (Paraguaypresent); Venezuela (Venezuelapresent) W. Malesia: present W. Polynesia: present W., Central and S. China: present tropical South Asia: present
About 56 genera with c. 300 spp., all woody, predominantly in the tropics, rapidly decreasing in number towards the subtropics; 5 genera with part of their species in the temperate zones of Africa, Asia, Australia and S. America.
In Malesia a total of c. 100 spp. in 21 genera, of which 3 are strictly endemic, viz Cantleya (W. Malesia), Hartleya and Pseudobotrys (both in New Guinea); 8 other genera find their main area of distribution and generally their greatest number of species in Malesia, but occur also in parts of S. and SE. Asia, viz Gonocaryum, Platea (both also in New Britain), Codiocarpus, Stemonurus (also in the Solomon Is.), Miquelia, Nothapodytes, Phytocrene, and Sarcostigma; 3 genera, viz Apodytes, Iodes and Pyrenacantha, are found in Africa (also Madagascar), SE. Asia and Malesia. The genus Citronella is amphipacific (Malesia, E. Australia, Melanesia, New Caledonia, New Hebrides, Fiji, Samoa, Tonga, Costa Rica, Venezuela, Brazil, Paraguay, N. Argentina, Bolivia, and Central Chile); 6 genera, viz Gomphandra, Medusanthera, Merrilliodendron, Polyporandra, Rhyticaryum, and Stemonurus, extend from Malesia into Micronesia and Melanesia or even W. Polynesia; of these only Gomphandra and Rhyticaryum are also found in NE. Australia. Whitmorea, so far known, is limited to the Solomon Is., but might occur also in SE. New Guinea.
Icacinaceae of Malesia show a strong affinity with those of tropical South Asia (SW. India, Ceylon) and Southeast Asia (Sikkim to Assam, Bengal, Burma, Thailand, Indo-China, W., Central and S. China incl. Hainan and Formosa, S. Japan). Most of the members of the family in Australia point to an Asiatic-Malesian origin; Irvingbaileya, limited to Queensland, is taxonomically very close to Codiocarpus and Medusanthera. Pennantia in New Zealand and on Norfolk I. is more distinct from the Asiatic-Malesian bloc of genera. New Caledonia has, besides Citronella, 2 endemic genera, viz Anisomallon (allied to Apodytes) and Gastrolepis (related to the group of genera around Medusanthera).

Dispersal

Little is known of the dispersal of fruits, part of which are eaten by wild animals (e.g. of Gonocaryum, Cantleya, Gomphandra, Medusanthera). Buoyancy of fruits is certain for Merrillioden-dron, less so for Gonocaryum and Stemonurus, and may have contributed to their dispersal.

Taxonomy

Four of the genera found in Asia and Malesia were revised by R. A. HOWARD (Cantleya: ; Codiocarpus: ; Medusanthera: ; Nothapodytes: ); these revisions were based on rather scarce materials as far as Malesia is concerned. A precursory paper with revisions of most of the genera concerned and based on practically all Asiatic and Malesian specimens available today was published by myself in , supplementing my previous studies on the family ().

Uses

In Malesia but a few tree species grow to big dimension with a clear bole (Cantleya, Stemonurus, Platea). Of these only Cantleya corniculata (BECC.) HOWARD has a marketing value and is exported from Sarawak and Brunei. Icacinaceae have a hard or mostly rather soft, often whitish or cream, sometimes aromatic wood, and are apparently only locally used by the natives, as can be deduced from the many vernacular names known.
The leaves of Rhyticaryum species are eaten as a vegetable. Medicinal use is recorded for several species but needs confirmation. The seeds of Cantleya, Phytocrene, Stemonurus and Sarcostigma are edible, but of a poor quality. The stems of lianas (Miquelia, Phytocrene) hold fresh edible water.

Phytochemo

The few chemical data available about the chemistry of this family were summarized in my . In the meantime, oleanolic acid was isolated from the bark of Apodytes dimidiata E. MEYER (= A. beddomei MAST.). The scanty chemical information available about Icacinaceae at this time, prevents a chemotaxonomic discussion. — R. HEGNAUER.