Studies on the Cytology of some Species of Taraxacum. 461 
the anaphase of the first mitosis, in which one embryo-sac-mother-cell 
was cut in three serial sections raore or less obliqnely; in the upper group 
of chromosomes we may easily count at least 38 ehromosomes. So the 
first nuclear division of the embryo-sac-mother-cell appears to be the 
homotypic division, but not the reducing one. 
Soon afterwards a nuclear membrane and nucleoli appear in both 
daughter-nuclei, being followed by the formation of a cell-wall between 
them. Thus two megaspores are produced (Fig. 73). The seeond nuclear 
division, which gives rise to a row of four megaspores in the case of T. 
platyearpum, does not take place liere at all. The lower or chalazal me- 
gaspore, on the contrary, begins to enlarge at once, compressing the upper 
or micropylar one, which now shows signs of disintegration (Fig. 74). 
The cytoplasm becomes denser and stains deeply and the nuclei also 
lose their definite outline, being followed by the complete degeneration 
of the upper cell, which remains for a time as a dark cap at the summit 
of the embryo-sac (Fig. 75). The lower cell enlarges gradually and de- 
velops directly into the embryo-sac. 
The further development of the latter is similar to that of T. platy- 
carpum and we may scarcely find any deviation. At a certain time tlie 
nucleus of the lower functional megaspore divides by mitosis and the 
two daughter-nuclei thus formed undergo two successive divisions, thus 
producing a normal eight-nucleated embryo-sac. The mature embryo- 
sac has the same construction as that of T. platyearpum, but is excee- 
dingly larger than that of the latter. Fig. 76 shows an embryo-sac, in 
which the primary endosperm-nucleus has alreadv undergone few mitoses, 
while the egg nucleus yet remains undivided; three antipodal cells and 
two synergids (one of which is shown in the figure) are recognizable, 
but the former shows the indication of disintegration. In these or earlier 
stages of the embryo-sac I could never found any pollen-tube in the 
micropylar portion; moreover the synergids were found intact in many 
cases, even when the embryo has reached the eight-or more-celled stage. 
When the ovum-cell undergoes its first division, we may count alreadv 
several dozen endosperm-nuclei. 
III. Discussion. 
a) Irregularities in the pollen-development. 
In the pollen-development of T. albidum there occur many irregularities 
and abnormalities, which lead to the production of irregulär pollen-grains, 
while in T. platyearpum it goes quite normally, as already mentioned. 
