Symplocos

Description

Shrubs to (rarely) large, (in Mal.) evergreen trees; Leaves simple, alternate or spirally arranged, rarely pseudoverticillate, estipulate, penninerved, petioled, rarely almost sessile; Flowers in spikes, racemes, or panicles, mostly from the upper leaf-axils, sometimes condensed to clusters, sometimes terminal or from the axils of fallen leaves, rarely solitary; Stamens 4 to mostly ∞, connate in a long monadelphous tube, at its base adnate to the corolla and very unequal, but in subg. Hopea only connate at the very base, monadelphous or pentadelphous and then the bundles alternipetalous; Ovary inferior (to ± semi-inferior), 2-5-celled, with a complete septation; Ovules 2-4 in each cell, pendulous, anatropous-epitropous or amphitropous, unitegmic, tenuicellular. Seeds straight or curved, 1 in each developed cell, with copious endosperm;

Distribution

Asia-Tropical: Australasia:, New South Wales (New South Walespresent) Bombay: present Ceylon: present Deccan: present Lord Howe I. at 32° S: present Manchuria at 46° N: present New World: present Northern America:, Washington (Washingtonpresent) Pacific:, Fiji (Fijipresent) S. Brasil: present U.S.A: present West Polynesia: present eastern parts of the Old World: present
About 250 spp., in the eastern parts of the Old World, from Ceylon and Bombay in the Deccan to Fiji in West Polynesia and from Manchuria at 46° N as far as New South Wales and Lord Howe I. at 32° S; in the New World from the State of Washington in the U.S.A. to S. Brasil; throughout Malesia. .
There is no species common to the Old and New World, but the E. Asian S. lucida is closest allied to the N. American S. tinctoria.

Ecology


Pollination

DOCTERS VAN LEEUWEN () reported of S. cochinchinensis var. sessifolia, on the summit of Mt Pangrango, West Java, at c. 3000 m, that flowers expand in the morning but open only halfway, the corolla remaining bent over the sexual organs; at 8 h. anthers are open and often touch the stigma on which the sticky pollen readily falls; on the 2nd flowering day the corolla is widely open, anthers are empty, and the stigma is always pollinated. This means self-pollination. DOCTERS VAN LEEUWEN found, however, also the flowers frequented by various insects, among them bees and bumblebees. They are not so much attracted by the little nectar, but are in search of pollen.

Some species may have locally a strict flowering time; e.g. S. cochinchinensis var. sessifolia flowers, according to DOCTERS VAN LEEUWEN (l.c., fig. 52), from October to January, in the rainy season, on the summit of Mt Pangrango, West Java.

Dispersal

RIDLEY (Disp. 1930) assumed that bats may be fond of the hard-fleshed drupes (l.c. 347). He mentioned that in North America tyrant birds (Sayornisphoebe) eat amongst others fruit of S. tinctoria (l.c. 483) and that in South America a curassow, a sort of turkey, would feed on the fruit of S. cernua. DOCTERS VAN LEEUWEN () believed Symplocos to be dispersed by birds but did not find endocarps in the stomach of fruit-eating birds. VAN STEENIS found fruit of S. henschelii abundant on the ground below trees at Tjibodas, although this species has a fairly thick, hard-fleshed exocarp, in contrast to most species in which the exocarp is thin. Also in fossils sometimes immense quantities of stones are found together, about which KIRCHHEIMER reported (): in a total mass of c. 3500 m3 he estimated the number of endocarps at some 2½ billions. He assumed that these were deposited within one century in a site of forest dominated by Symplocos. However, he added that the layers in which the endocarps were deposited gave no evidence of rivers which could have transported and accumulated the seeds and he concluded that they have dropped to the soil in situ. For these reasons abundant dispersal by birds or bats is in Symplocos not very likely.

Dispersal by water takes place in species in which some fruit cells are barren and remain empty, e.g. S. celastrifolia.

Morphology

The phyllotaxis is variable but constant for the species; it is either spiral or alternate (distichous) in which latter case the twigs are often zigzag ().

In most species leaves are more or less equally dispersed along the twigs, but in other species there is a tendency that the leaves are becoming crowded towards the end of the year's growth, e.g. in S. macrocarpa, as noted by TRIMEN (). In Malesian spp. this occurs also in S. herzogii and S. gigantifolia where the large leaves occur crowded at the end of the year's growth.

There is a single species in which all the leaves are in real pseudo-whorls, viz S. verticillifolia from the Philippine Is. ().

The leader-shoots in Symplocos, e.g. S. fasciculata, have spiral phyllotaxis; such shoots may, however, also carry flowers.

Rejuvenation is in certain species by continuous growth of the twig apex, as is e.g. characteristic in S. fasciculata. In other species, however, there are clear buds with conspicuous bud-scales, indicating that the growth mode is flush wise and discontinuous, as e.g. in S. costata and S. lucida (). This might be a good character of subdividing subg. Hopea. It can, however, only be used if one has accurate knowledge of the rejuvenation process of each species. This is sometimes difficult to ascertain from herbarium material as the bud-scales do not always leave traces of distinct scars, field data hardly ever mention the character, and material is seldom collected in the stage of flush. If the growth mode were well examined in all species I believe it would represent a good key character.

Flushwise, discontinuous growth, with scaly buds could be assumed to be an adaptation to seasonally cold climates. It is a life form intermediate halfway evergreen and deciduous. It is rare in the Malesian tropics where it is known e.g. from Acer, some genera of Lauraceae, Fagaceae, which also in the tropics are found in the cool, tropical-montane climate, which is however hardly seasonal. It still could be viewed as an indication of former immigration of taxa of higher latitude. Once acquired this growth mode must then have been conserved, as it occurs also in S. barring-toniifolia which is restricted to the tropical lowland.

The inflorescence is either a panicle or a raceme or spike. Morphologically it is cymose, the flower always being sustained by two bracteoles which may at times carry abortive buds in their axil (). In some cases the inflorescence is condensed to a fascicle or cluster of flowers () or even be reduced to a single flower (). In a few species flowers occur on old wood, as e.g. in S. polyandra, S. wikstroemifolia (p.p.), S. rubiginosa, and S. tricoccata.

The flowers are bisexual but functionally unisexual flowers are found in several taxa, especially in New Guinea. Such taxa are either dioecious or polygamous. In male flowers the style is small and without a stigma, in female flowers the number of stamens is reduced (even to less than 10) and anthers are sterile. In subg. Symplocos the stamens are monadelphous with a long tube (); in subg. Hopea they are only connate at the base for at most 2 mm (), and intergrading from strictly monadelphous to strictly pentadelphous, the phalanges being alterni-petalous.

In my revision it has been explained that, in contrast with former opinion, the ovary is initially 1-celled, with the ovules attached close to the centre on the induplicate part of the carpels, each of the 2-5 compartments having usually 4 ovules; in fruit these appear as cells. In each developed cell there is usually one seed. The latter and the embryo it contains may be curved or straight. See .

The fruit is a drupe, with a fleshy, corky or woody mesocarp and a very hard stone (endocarp). The endocarp may be smooth (, ) or show outside ridges or irregularities (, , , ); the same holds for the inside of the endocarp. In the centre of the copious endosperm the embryo is embedded. It is slender and may be straight or curved. In the tropical subg. Symplocos it is always straight. In subg. Hopea it is straight in all American spp. and in 80% of the living species in the Old World and also in all fossil species in Europe. From this it is concluded that a straight embryo seems to be the primitive state in the genus. Only the three Pliocene fossil species of Japan, which can be matched with living species, have curved seeds and consequently curved embryos.

Curved seeds occur in degree, they may be hook-shaped or U-shaped or even be twice curved (S-shaped in S. brachybotrys). See . This may give some difficulty in studying sections of the stones to count the number of seeds in a fruit (e.g. h-h/).

Although of the living species only 20 % have curved seeds the vast majority of the individual living plants have curved seeds; so it seems that this probably recent trend in the evolution of the genus was successful although the reason for its origin and advantage of its function remains obscure.

Anatomy

For general surveys also covering the older literature, see .

Taxonomy

BRAND (1901) has made an intricate subdivision of the genus, partly based on former generic names. I believe we cannot go further than a subdivision into two subgenera, in which macromorphology is supported by chemotaxonomy and palynology, viz subg. Symplocos and subg. Hopea.

Subdivisions could be based on one important single character: straight versus curved embryo, spiral versus distichous phyllotaxis, continuous versus flushwise growth from scaly buds, but it appears that such subdivisions do not coincide. This leads to the view that there is a block of species with reticulate affinities. This view also emerges from the palynological results.

Both subgenera occur in the New and the Old World; subg. Symplocos, which is almost strictly tropical, possesses only 2 spp. in Indo-Malesia, but probably many more in America.

In this revision 58 spp. are distinguished in Malesia; there are more new species, but I have refrained from describing them as the material is incomplete; I have enumerated them in my revision l.c. 296.

Cytology

In my monograph I have given an account of chromosome numbers, which are unfortunately too few. However, the majority is n = 11, with some deviations; rarely 2n = 24, and one count of the North American S. tinctoria of In = 14, all in subg. Hopea. The one count known of subg. Symplocos in Malesia yielded 2n = c. 90 (2n = 88 would fit an octoploid). It would be too rash to conclude that polyploidy would be normal in that subgenus.

On the other hand it may tentatively be concluded that species in subg. Hopea are diploid, with×= 11. This does not fit the numbers found in other Ebenales families, nor in Theaceae, but it does agree with Cornaceae sensu lat.

Uses

As timber Symplocos has no great value, according to HEYNE (). Leaves and bark of Symplocos contain a fair amount of alum, both in Asian and American spp. (cf. ). This was commonly used, mostly from decoctions of the bark, in dyeing processes (red and brown), e.g. in the batik industry in Java. RUMPHIUS already mentioned this use from the Moluccas. Several species were used for this purpose, e.g. S. cochinchinensis, S. fasciculata, S. odoratissima (HEYNE, l.c.). The same compound is probably also the constituent active in medicinal uses against so-called sprue ('thrush') as 'obat seriawarf.

Notes

Identification of material of Symplocos is for several reasons far from easy. Because of simultaneous flowering flowers and fruits are practically never found together and both stages are properly needed. Only few species possess well definable vegetative characters. Moreover, a few widespread species have proved to be rather variable, to a fair degree by racial differentiation. These are the reasons that besides a general key in which all characters are used, I have found it useful to add a number of partial keys for islands or island groups in a double series, either for fruiting or for flowering material.

In .

Citation

JACQ., Select. Stirp. Am. Hist. 1763: t. 175, f. 68
BRAND - in Pfl. R. Heft. 1901: 9 fig.
NOOT. - in Leid. Bot. Ser. 1975: 7 fig., 21 pl., with full synonymy.
MIERS - in J. Linn. Soc. Bot. 1879: 285
LINNE, Gen. Pl, ed. 6. 1764: 272

Synonymy

Symplocos JACQ., En. Fl. Carib.: 5, 24. 1760

    Keys