The behavior of plastids during the life-cycle of plant has some regularities. 1)The increase and decrease of the number of plastids shows some regularities during oogenesis, spermatogenesis, sporogenesis or spore germination. In some cases many plastids decrease in number and only one plastid remains in the definite cell and in other cases, vice versa. 2) When the cell divides which has only one plastid and a nucleus, the plastid divides at first and then the nucleus divides. So the resulted daughter cells contain one nucleus and one plastid respectively. The plastid always precede the nuclear division. 3) When the spore-mother cell completes reduction division, which has only one plastid and nucleus, the plastid divides at first into four and then the nucleus complets the reduction division. So the resulted four spores contain one plastid and one nucleus respectively. 4) The plastids in fertilized egg-cell, which are derived from the egg-cell and the spermatozoid or sperm-cell, fuse each other in some species and remain separately in other species. 5) During the fertilization, the spermatozoid brings its own plastid (plastids) into the egg-cell in some species and do not bring in the other species. Besides these regularities, the plastids contain DNA in some plants (Ris and Plaut, 1958; Iwamura, 1962; Ishida, 1964; Bisulputra and Bisulputra, 1967; Woodcock and Fernández-Moran, 1968) and the plastid increases its number by division. Therefore, the plastid is thought to be self-replicating system and its behavior is supposed to be independent from the nuclear action. The independence of the behavior of plastid from the nucleus, to some extent, has already been advocated by Yuasa (1952), Yoshida (1953) and Ueda (1949, 1949). The division of plastid has already been found, and confirmed by Strasburger (1880), Haberlandt (1882, 1888), Nägeli (1863), Sachs (1875), Schmitz (1882), Nemec (1910), Scherrer (1914), Carter (1919, 1921) Kiyohara (1926), Ma (1928), Senjaninova (1928), Stone (1932), Reinhard (1933), and Kusunoki and Kawasaki (1936), Yuasa (1945, 1947, 1950) has also observed the regularities of the division of plastid in Selaginella uncinata. The distribution of plastids into cells during the life-cycle of plant is thought to show some regularities, considered from the above-mentioned facts, but the detailed features of these regularities should be left for a future research.