Myrtaceae A (Eucalptus & Melaleuca)

Genera: Eucalyptus, Melaleuca

Vouchers:   E. coolabah JAB100, JAB107, JAB133, JAB137, E. populnea JAB159, JAB170, E. ochrophloia JAB161, E. thozetiana JAB163, E. camaldulensis var. obtusa JAB191, M. trichostachya JAB144, M. glomerata JAB191

Family:  Myrtaceae

General features:  Density 800-1300 kg/m3.   Heartwood red, reddish-brown or brown and darker than sapwood.  Gum deposits visible on JAB191 E. camaldulensis var. obtusa specimen.  White deposits visible on JAB161 E. ochrophloia specimen.

Microscopic features:

Vessels  Tangential vessel diameter: range 10-125 µm; mean 60 µm; SD 21 µm; average maximum 32-106 µm; n =  2276 vessels.  Vessels per square millimetre: range 13-284 vessels per mm2;  n =  63 sampled areas.  Vessels solitary.  Perforation plates simple without prominent rim.  Vessel to vessel pits vestured. 

*Fibres/tracheids  With numerous, distinctly bordered pits present.

Axial parenchyma  Axial parenchyma apotracheal and paratracheal.  Apotracheal axial parenchyma diffuse to diffuse-in-aggregate.  Paratracheal axial parenchyma scanty to vasicentric.  

Rays Rays 1-4 cells wide with uniseriate rays present (n = 1739 rays).  Rays of uniform width and not wider than vessels.  Rays 4-28 per tangential mm (n =   99 sampled areas).  Ray height: range 36-420 µm; mean 129 µm; SD 47 µm; n =   1253 rays.   Rays heterocellular or homocellular?  Tyloses present in heartwood.  Abundant white deposits may be present in heartwood.

Helical thickenings  Absent.

Physical and chemical tests:   Chrome azurol-s test negative.   Heartwood fluorescence present or absent.  Froth test weakly positive to positive or weakly positive to negative.   Ethanol extract fluorescence absent.  Ethanol extract discoloured or colourless.  Water extract discoloured.   Water extract fluorescence absent.

Notes:  Eucalyptus and Melaleuca is distinguished from Corymbia by the presence of solitary vessels and distinct and numerous bordered pits.  Absence of tyloses is not diagnostic and their presence is recorded only where they are abundant in heartwood (IAWA 1989: 261).

* At this stage the key makes no distinction between fibres and tracheids as they are difficult to tell apart and there is some confusion in the wood anatomical literature as to their definitions in hardwoods (IAWA: 264). For example, the taxa for which this character was predominantly included - Myrtaceae A (Eucalyptus & Melaleuca) - contain numerous, conspicuous bordered pits that are both called fibre tracheids (Dadswell 1972: 21) and vasicentric tracheids (IAWA: 262).