Linospadix linospadix

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Linospadix - the walking-stick palms - in Australia and New Guinea:

The genus Linospadix is distributed along most of the north-east coast of Australia and throughout most of the island of New Guinea. In north Australia it occurs in Qeensland from Mcllwraith Range south to Mission Beach, and in eastern Australia in southern Queensland from near Gympie south to Hastings River in northern New South Wales. This account recognises seven species in the genus, five in Australia and two in New Guinea.

Species of Linospadix are commonly known as the walking-stick palms, due to the former utilisation of the stem for walking-sticks. Mueller (1885) provided the first account of the use of Linospadix species for this purpose..."Bacularia monostachya (=Linospadix monostachya): Eastern Australia, extending to extra-tropical latitudes. One of the best among small palms for table decoration. The stems sought for walking-sticks." The making of walking-sticks from the stems of Linospadix has not been practised since the years immediately following WW2. Apart from the consumption of fruits of both Australian and New Guinea species by indigenous people, no other uses for Linospadix species have been recorded. Horticulturally, Linospadix species are not that commonly used as they are relatively slow growing and not readily adaptable to cultivation due to their often specific cultural requirements of shade and humidity. Of the species in cultivation, L. monostachya and L. minor are the most common as they have a wider ecological amplitude than the other species.

Taxonomic History:

The genus Linospadix was first described by Wendland (1875), and included one species, L. monostachya. The identity of the genus was soon to become obscured by new species described firstly by Beccari (1877) and secondly by the creation of a genus, Bacularia, first suggested by Mueller (1870) and later defined by Hooker (1882). Beccari's interpretation of Linospadix differed considerably from the original description, and the species that he included in his Linospadix are now known to be species of Calyptrocalyx (= syn. Paralinospadix). The fate of Bacularia was for it to include species that conformed to Wendland's original description. At first, only Australian taxa were included in Bacularia, but Beccari later described a few species also from New Guinea. This situation continued until Burtel (1935) recognised the inconsistencies within the suite of taxa. He proposed a revision of Linospadix, which included the synonymisation of Bacularia under Linospadix and the creation of a new genus, Paralinospadix, to account for the New Guinea taxa that Beccari had 'inadvertently' described as Linospadix species. Burret's revision is the currently accepted taxonomy for Linospadix.

Recently, Dowe & Irvine (1997) presented a revision of Linospadix in Australia in which one new species was described. The New Guinea taxa are presently the subject of a systematic revision (Dowe in prep. ). and preliminary assessment indicates that of the five species that have been described for the island, they indeed represent only two closely related species, and informal synonymy is accordingly suggested. A full account of the Linospadicinae is now being prepared as part of the Flora Malesiana project (Dowe & Ferrero in prep.).

Linospadix and Its Relatives:

Linospadix (7 spp.) is included in the subtribe Linospadicinae with four other genera - Calyptrocalyx (20 spp.), Howea (2 spp.), Laccospadix (1 sp.) and Paralinospadix (24 spp.). Of the Linospadicinae species, 45 are endemic to New Guinea and the remainder to the Moluccas (1 sp.), Australia (6 spp.) and Lord Howe Island (2 spp.). Preliminary phenetic and cladistic studies suggest that Calyptrocalyx and Paralinospadix are indistinguishable from each other; Howea and Laccospadix are very close to each other though separable; and Linospadix is relatively isolated from the other genera by what are perceived as the most taxonomically and biologically important characters within the group. If closest relatives were to be suggested for Linospadix, they would include both Howea and Laccospadix due to similarities in the following features:

a. the position at which the peduncular bract is attached - it is relatively close in the three genera

b. the peduncular bract fully encloses the inflorescence during.development in all three genera (not so in Calyptrocalyx/Paralinospadtx)

c. floral morphology - all three genera have staminate mowers with basi- or subbasi-fixed. non-versatile anthers and short filaments (dorsi-fixed and versatile in Calyptrocalyx/Paralinospadix).

Bract attachment positions:

The position of attachment of the peduncular bract is one of the primary characters that separates genera in the Linospadicinae. In all genera, the prophyll (lower bract on the peduncle) is attached at the base of the peduncle: it is the position of attachment of the peduncular bract (upper bract on the peduncle) that differs among genera. In Calyptrocalyx/Paralinospadix the peduncular bract is attached immediately adjacent to the prophyll, and the developing infiorescence becomes exposed with the distal portion breaking through while still in immature bud. In Howea and Laccospadix, the peduncular bract is attached about midway between where the prophyll is attached and the lowest flowers on the rachilla (flower bearing portion of the infiorescence). The peduncular bract fully encloses the infiorescence, with the rachilla only becoming exposed upon disintegration of the bract, though the bract still remains attached and is never shed. In Linospadix, the peduncular bract is attached at the extreme distal end of the peduncle, and therefore a considerable portion of the peduncle is exposed. As the inflorescence develops, the rachilla remains fully enclosed within the peduncular bract. At, or just prior to maturity of the flowers, the peduncular bract withers and is shed, leaving a more or less clean scar at the base of the rachilla.

Other Generic Differences:

Other generic differences that distinguish Linospadix from its relatives are not as clear-cut as is the case with bract attachment. For example, characters of habit (solitary or clustering), fruit shape (globose or elongate), and condition of the mesocarp (fibrous or non-fibrous) and the endosperm (homogeneous or ruminate), cannot be used with certainty for taxonomic purposes. Floral differences within the related genera display two classes:

Calyptrocalyx/Paralinospadix usually possess staminate flowers with an extended pistillode and stamens with dorsi-fxed, versatile anthers on long filaments. In Howea, Laccospadix and Linospadix, staminate flowers lack a pistillode or it is only small, and stamens have basi-fixed to subbasi-fixed, non-versatile anthers on short filaments. These last three genera are further distinguished by the condition of the endosperm - it is homogemous in Howea and Linospadix, and ruminate in Laccospadix - and the position of attachment of the peduncular bract is as described above.

Ecology:

All species of Linospadix occur in moist closed forests that lack a significant seasonal dry period. Rainfall is above 1200 mm and as high as 10000 mm per annum in some of these forests. In Australia, the genus occurs from sea-level up to 1600 m altitude; in New Guinea, it is most common at 200-1000 m altitude, and uncommon at 0-200 m and above 1000 m altitude. Very little is known about the ecology of the genus, though it has been observed that it has traits that suggest that it is anemophilous (insect pollinated) and that it is protandrous (Henderson 1986). As for phenology (periodicity of floral events), there is a considerable period of time between staminate anthesis (pollen shedding phase) and pistilate receptivity on an individual inflorescence. Preliminary observations suggest that the lag time may be up to 12 months for L. monostachya and at least many months for other Australian species. Population ecology, reproductive biology and genetic diversity are essentially unknown for the genus, and are areas of study that could yield interesting results.

Genetic description of Linospadix:

Clustering or solitary, small, pleonanthic, monoecious palms. Stems slender, nodes conspicuous; internodes elongate. Leaves bifid, or irregularly or evenly segmented; leafbase clasping, crownshaft not developed; petiole elongate or absent, channelled adaxially, rounded abaxially; pinnae single or united, apices praemorse when united. acuminate when not united. Inforescence protandrous, interfoliar, solitary, spicate: peduncle elongate, erect; prophyll laterally compressed, attached as base of peduncle. enclosing inflorescence in bud, persistent: peduncular bract tubular, attached at tip of peduncle, deciduous; rachilla ca. length of peduncle to much less. Flowers spirally arranged in shallow pits; triads in proximal portion, paired or solitary staminate flowers in distal portion. Staminate flower sessile, symmetric in bud; sepals broadly imbricate; petals ca. twice as long as sepals, thick, apically valvate; stamens erect, 4-20, filaments short, anthers sagittate, subbasito approaching basi-fixed, latrorse; pollen elliptic, monosulcate, exine tectate, finely reticulate; pistillode absent or small. Pistillate flower globular, larger than the staminate flower; sepals broadly imbricate; petals exceeding the sepals, thickened valvate tips; staminodes 3-6, toothlike; stigmas 3, recurved. Fruit ellipsoid, cylindri- cal, globose or pyriform, yellow or red at maturity; stigmatic remains apical; epicarp smooth, striate or rugose; mesocarp fleshy, thin, longitudinal fibres appressed to endocarp; endocarp thin, adhering to the seed; seed subbasally attached, raphe attached for less than o length of seed; endosperm homogeneous; embryo basal. Germination adjacent-ligular. Eophyll bifid. n = 16.


Contributed by:

John Dowe (Text - from Palms & Cycads No. 58, Jan-Mar 1998)


External Links:

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