Studies on the Cytology of some Species of Taraxacum. 
455 
like bodies, very angular or uneven in their outline; and they are very 
irregulär in shape, being variously twisted. Fig. 29 shows a nucleus at 
a little later stage, when the ehromosomes appear shorter and thicker. 
The condensation and contraction proceed further, until finally the sphe- 
rieal or granulär ehromosomes are produced (Figs. 30 — 32). 
The number of ehromosomes were counted in this diakinesis stage 
and it proved to be eight for the gametophyte. 
Figs. 33 — 34 show the first division of the embryo-sac-mother-cell, 
where eight paired ehromosomes are arranged at the equatorial plate 
of the bipolar spindle. When the contraction of the spindle fibres takes 
place the paired ehromosomes separate from each other and pass to the 
respective poles of the spindle, and then we find that each group of 
ehromosomes shows distinctly eight of them (Fig. 35). So the first 
nuclear division of the embryo-sac-mother-cell must be a heterotypic 
and reducing one, as in the pollen-mother-cell. At the anaphase of the 
first division the ehromosomes become amoeboid in shape, and enter 
into the more or less anastomosing condition and it is followed by the 
formation of a cell-wall between these two daughter-nuclei, separating 
the original cell into nearly two equal ones (Fig. 36). 
Shortly afterwards the two spindles appear simultaneously in both 
daughter-cells derived by the heterotypic mitosis and each chromosome 
arranges regularly in pair on the equatorial plate (Fig. 37). This mitosis 
is the homotypic division. In the telophase of the sec-ond division each 
chromosome yet maintains its respective identity. Then the cell-walls 
are produced between these four nuclei, forming a row of four mega- 
spores (Fig. 38). At first they are nearly ecpial in size, but soon 
afterwards the lowermost one enlarges rapidly, consuming the upper 
three cells, which go gradually to degeneration. In more advanced 
stage these micropylar three cells are often observable as cap-shaped 
bodies upon the functional large megaspore and stain deeply with 
haematoxylin. 
The further development of the functional megaspore takes place 
in the usual manner and we see scarcely any deviation. The cell enlarges 
gradually and many vacuoles appear in the cytoplasm. Then the nucleus 
divides once more by mitosis and these two daughter-nuclei move to- 
wards the opposite poles of the sac, which have a large central vacuole 
(Fig. 39). The two daughter-nuclei then divide simultaneously by mitosis 
and give rise to four nuclei, each of which undergoes once more the nu- 
clear division, thus producing a typical eight-nucleated embryo-sac. At 
this stage the cytoplasm is visible as a thin layer in the periphery of the 
