WOODS OF EUCALYPTUS .1. DISTINGUISHING 3 SPECIES FROM THE ASH GROUP (EUCALYPTUS-REGNANS, EUCALYPTUS-DELEGATENSIS AND EUCALYPTUS-OBLIQUA)

In Australia the ash group of eucalypts comprises approximately 35 spe cies of Eucalyptus from the botanical series Obliquae. They are abunda nt in south-eastern Australia, but timber of commerce comes mainly fro m Victoria and Tasmania and includes E. regnans F. Muell., E. delegate nsis sis R.T. Baker and E. obliqua L'Herit. This group produces some o f the fastest growing and the highest yielding hardwood species in Aus tralia. The timbers are similar in appearance and can be interchanged for many uses, but there are some important differences. This study fo und 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. Diffe rences between mainland and Tasmanian provenances were also observed. Growth rings are prominent in E. delegatensis from the mainland, but l ess so from Tasmania, and least distinct in E. obliqua. Basic density can be used to distinguish E. obliqua when samples are heavier than 60 5 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. obl iqua, whereas it is 1-5, mostly 1-2(-4) cells high in the other two sp ecies; 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. delegaten sis, 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, mostl y 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.