In order to make clear the historic changes of subspecies of rice cultivated in the ancientry in the lower reaches of the Changjiang River, analysis of plant opal was carried out for Loujiaqiao site in Zhengjiang province, China. It was identified that rice have been cultivated there since about 6000 years ago by detecting a great number of plant opals in soil samples and earthenware fragments from this site. Further, analysis of morphological characteristics of the plant opals of rice showed that the vertical, horizontal and lateral lengths had rise and the b/a had fell with changes of historic times, but there were some times such as the early period of the Hemudu culture dating from 5000 B.C. to 3900 B.C. and the Maqiao-Shangzhou period dating from 1700B.C. to 770B.C. when the changes were the opposite to those. Changes of discrimination scores appeared to be same as those of vertical, horizontal and lateral lengths, but those of the periods of the Hemudu culture were numerically smaller than 0.5, appeared neuter. From those result, it was proposed that the rice was varied in the periods of the Hemudu culture and would change to a great deal cultivated japonica rice from then on, but there was possibility of developing of indica rice, during those times.
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