XVI International Botanical Congess

Tree trunks of 10 coniferous tree species (one tree each) growing in the experimental field were knife-marked every two weeks from July of 1994 to the end of 1996 except winters. The traumatic tissues were analyzed microscopically and the seasons of the transition-wood formation were investigated.The transition-wood in Larix kaempferi and Pseudotsuga menziesii, which latewoods are wide and the transition are very abrupt, were formed in late-June regardless to the difference of deciduous or evergreen. Those in Picea sitchensis and Cunnighamia lanceolata, very narrow and very gradual, were formed in late-August. In the others, Pinus densiflora, P. strobus, and Abies firma (wide and abrupt to gradual) they were formed in mid- to late-June, as the same as Sequoia sempervirens, Methasequoia glypterostoboides and Cupressus lustania (narrow and gradual).