Abstract
Plant opal, a plant-derived silica body (SiO2) excavated from archaeological sites, has been used to analyze various characteristics of past vegetation and crops relevant to the archaeological and palaeobotanical studies. We attempted to distinguish japonica varieties from indica ones based on the morphological features of the silica body extracted from living leaves of rice cultivars, so as to establish a methodology to determine whether plant opal was derived from indica or japonica varieties. In the present experiment, ninety-six cultivars classified into indica and japonica by SATO's discriminant function (Z2, see SATO et al. 1986) were exarnined. Silica bodies were extracted from living leaves, and four dimensions shown in Fig. 1 (a, b, c and d) were measured for 50 samples of each cultivar. Silica bodies were classified into the α-type (smaller a, b and d, and larger b/a) and β-type (reverse of α-type, see Fig. 1 FUJIWARA, 1976). A preliminary test revealed that the silica bodies of typical indica showed the α-type, while those of typical japonica the β-type. To represent the varietal variaiton in the shape of the silica body, the discriminant function Z1 was calculated as follows: Zl=0.049 (a+b)-0.019 (c)+0.197 (d)-4.792 (b/a)-2.614
