Woods of eucalyptus .1. Distinguishing three species from the ash group (E-regnans, E-delegatensis and E-obliqua)

In Australia the ash group of eucalypts comprises approximately 35 species of Eucalyptus from the botanical series Obliquae. They are abundant in south-eastern Australia, but timber of commerce comes mainly from Victoria and Tasmania and includes E. regnans F. Muell., E. delegatensis sis R.T. Baker and E. obliqua L'Herit. This group produces some of the fastest growing and the highest yielding hardwood species in Australia. The timbers are similar in appearance and can be interchanged for many uses, but there are some important differences. This study found differences between the species in basic density, distinctness of growth rings and pore grouping, ray width, proportion of multiseriate rays, and the height of the multiseriate proportion of the rays. Differences between mainland and Tasmanian provenances were also observed. Growth rings are prominent in E. delegatensis from the mainland, but less so from Tasmania, and least distinct in E. obliqua. Basic density can be used to distinguish E. obliqua when samples are heavier than 605 kg/m(3), and E. regnans for samples less than 390 kg/m(3). Height of the multiseriate portion of the rays is 1-9, mostly 5 cells in E. obliqua, whereas it is 1-5, mostly 1-2(-4) cells high in the other two species; maximum height of the multiseriate portion of the rays is 3-12, mostly 4-8 cells in E. obliqua, 1-6, mostly 1-2 cells in E. delegatensis, and 1-8, mostly 1-3 cells in E. regnans; width of individual ray cells 10-30 mu m, mostly 15-20 mu m in E obliqua, and 5-16 mu m, mostly 8-12 mu m in the other two species. A key for separation between the species is given and the similarities to other species are discussed. Other commercially important species will be dealt with subsequently.