Miyawaki observed the trees which traditionally grew around temples, shrines, and cemeteries in Japan, such as Japanese Blue Oak, Castanopsis cuspidata, Bamboo-leaf Oak, Japanese Chestnut trees, and Machilus tunbergii (a tree from the laurel family). He showed that they were native species, relics of the primary forest. At the same time, he noted that trees such as Japanese Cedar, Cypress and Larch Pine, supposedly native to Japan, had in fact been introduced into Japan over centuries by foresters in order to produce timber.