Flower buds varying in stages of development were harvested from tobacco plants (Nicotiana Tabacum). One of the five anthers from each flower bud was used to determine the stage of pollen development. According to this procedure all flower buds were classified into nine groups ranging from the stage of archesporial cells to that of mature pollen grains. The remaining anthers from each flower bud of every group were placed in a Erlenmeyer flask containing 40ml of solid tobacco C medium (Hildebrandt 1962) and then transferred to the modified RM-1964 medium (Linsmaier and Skoog 1965) containing 4 mg/l of kinetin and 2 mg/l of IAA. Fifteen days after the transfer, many embryoids appeared suddenly from the inside of dehisced anther which had been cultured from tetrad stage and these embryoids developed later into visible buds having dicotyledones. At the same time, callus was formed around the basal part of the buds. Forty five days later, numerous embryoids appeared from the proliferating callus. Chromosome counts conducted on a squashed preparation of the leaf primordia revealed that a young plant had 24 somatic chromosomes. This fact and that the embryoids appeared from the inside of dehisced anther and were easily removed from the wall suggest that they might be originated from developing germ cells. With regard to chromosome numbers of the plants, there are some possibilities that diploids or polyploids might appear from the proliferating callus. Microscopic observation of cultured germ cells revealed their morphological changes into the following types: 1) Ellipsoidal, shrivelled pollen grains, 2) Germinated pollen, grains, 3) Hypertrophied pollen grains with transparent cell walls and abundant starch grains, 4) Pollen grians developing into yellowish, multicellular bodies which later give rise to embryoids. It is very interesting that embryoids can be differentiated from germ cells at the tetrad stage. © 1968, The Genetics Society of Japan. All rights reserved.
