Abstract
In 1948, a dwarf semi-sterile rice plant was found from among a variety Ginbozu at the Faculty of Agriculture, Tokyo University. It may be a mutant from its peculiar characters. The chief characters are as follows. 1) The height of seedlings is a little shorter than normal from their short length of sheath, but late in maturity the stalks become much more shorter. The colour of leaves is darker, and near the top of blade appear remarkable wrinkles. 2) As only about one-third of spikelets produce small matured seeds and the culms are rigid, the ears stand upright at the harvest time and plants do not turn yellow. Consequently, many new branches or tillers are produced vigorously on the way to maturity even at higher nodes of culms. 3) The lowest node of a panicle seldom has lateral branches (often degenerate leaves) and seldom emerges from the sheath of boot-leaf. As the nodes in a panicle are few and the lateral branches are a little more than those of normal, each node except the lowest has more lateral branches, and the internodes are irregular in length. Arrangement of spikelets is also lacking in uniformity. 4) Flowers and seeds of normal shape are much smaller than those of normal plant, and lengthes of parts of flowers such as length of glumes, stamens are equally very short. Most flowers have relatively too small palea except a few extremely deformed ones having a longer palea than lemma, and there are various gradations of size of palea. As a result of this disproportion of size of both glumes, the hull does not close or fit tightly and sometimes remains open. 5) As anthers, pollens and pistils seem to be normel in their shape or size, sterility might chiefly be caused by the disproportion of size of glumes; during panicles are still in the sheath of boot-leaf, the anthers of flowers already disclosed are destroyed by water-drop in the sheath; after heading, the air gets in freely inside of glumes resulting in interference with the development of ovules fertilized by dryness, and often rain-drops also destroy the pollens before pollination. 6) The genetical studies of these characters are in progress.
