Studies on tlie Cytology of some Species of Taraxacum. 
465 
IV. Summary. 
1. By castrating flowers or by enclosing flower-heads in bags, T. 
platycarpum can produce no seeds, whereas T. albidum can produce 
many of them. 
2. In T. platycarpum, the number of chromosomes is eight for the 
gametophyte and sixteen for the sporophyte. 
3. In T. platycarpum, the first nuclear division of the pollen-mother- 
cell is the heterotypic and redueing one, while the seeond mitosis is the 
homotypic and equal one. Moreover there oecur no irregularities in 
their tetrad-division, producing normal pollen-grains. 
4. In T. platycarpum, the embryo-sac-mother-cell undergoes two 
successive divisions, one heterotypic and one homotypic, producing a row 
of four megaspores; the chalazal megaspore enlarges gradually and be- 
comes the embryo-sac. 
5. In T. albidum, the first nuclear division of the pollen-mother-cell 
may perliaps be either heterotypic or homotypic. ln the latter case, 
the seeond division often falls and produees then only two spores; in 
the former case, the seeond division is the homotypic one and several 
irregularities are often observable. 
6. In T. albidum, some of the pollen-grains disintegrate during their 
development, while others are very irregulär in their size and shape and 
appear to liave no germinating power. 
7. In T. albidum the embryo-sac-mother-cell undergoes no redueing 
division at all, but only one homotypic division, thus producing only 
two megaspores; of which one plaeed towards the chalaza becomes the 
embryo-sac. 
8. The number of chromosomes of T. albidum seems to lie between 
36—40. 
9. In T. albidum the oosphere can develop parthenogenetically. 
10. The volume of nuclei of the pollen-mother- cell in several species 
of Taraxacum seems nearly to be directly proportional to the number of 
their chromosomes. 
Tokyo, November 4, 1912. 
Archiv f. Zellforschung. X. 
31 
