Xylomelum is a genus of seven species in the plant familyProteaceae. The name derives from the Greek xylon and melon . They are native to Australia, growing in the form of tall shrubs and trees. The genus includes at least two species with the common name woody pear, Xylomelum pyriforme in the eastern states of Australia, and Xylomelum occidentale in Western Australia. Two species, Xylomelum angustifolium and Xylomelum occidentale, are endemic to Western Australia . The remaining species are found in NSW and Queensland. A detailed description of Xylomelum is found at .
Species
Xylomelum angustifolium ex J. Bot. Kew Gard. Misc. 4: 209
Xylomelum benthamiiOrchard J. Adelaide Bot. Gard. 21: 89
The fruits of Xylomelum are in the form of woody pears. When dried, these pears split down a central division, resulting in two halves. These "pears" are thought to have evolved primarily as a defense against seed predation. However, these woody fruits also provide protection of the seeds from fire. Johnson and Briggs consider the woody seeds in Proteaceae to be a late evolutionary adaptation to fire.
Distribution
A map of the recorded occurrences of Xylomelum may be found at
Classification
In 1788, Joseph Gaertner described the type species of Xylomelum as Banksia pyriformis, a species whose genus was effectively reclassified when James Edward Smith, in 1798, described the genus, Xylomelum, assigning it to the natural orderProteae of Jussieu. Smith gave the essential characters of Xylomelum as: flower spikes with simple scales, flowers with four petals bearing four stamens, with a blunt, club-shaped stigma, with a uni-locular capsule having two seeds, the seeds being winged. In 1811, Robert Brown, in On the Proteaceae of Jussieu , gave a key to the genera of Proteaceae. The key places Xylomelum in the group of Proteaceae which have dehiscent fruit, and are unilocular with two seeds, thereby grouping Anadenia, Grevillea, Hakea, Lambertia, Orites and Rhopala together. Within the group, Xylomelum is distinguished from Orites and Rhopala by having winged seeds, a thickened woody follicle with an excentriclocule, and a club-shaped stigma. Engler, in 1888, divided the Proteaceae into two sub-families, Persoonioideae & Grevilloideae, placing Xylomelum in Grevilloideae, and as being like Helicia in having the flower axis at the base with four glands, but differing from it by having the inflorescence in 'ears', not in loose 'grapes', and by having seeds with wings. Within the Proteaceae, Johnson & Briggs placed Xylomelum in the subfamily Grevilleoideae and the tribe Heliciaea. However, Weston & Barker, argue that within the tribe of Roupaleae, Xylomelum should be placed in the subtribe of Lambertiinae and not together with the Helicia (in the subtribe of Heliciinae, using in part, the evidence of the molecular studies of Hoot & Douglas, who pair Xylomelum with Lambertia. See Grevilleoideae for further discussion of the placement of Xylomelum within the Proteaceae.
