Overton—On the Boot Tips of Podophyllum Peltatum. 293 
studied, as shown in figure 19. Although the longitudinal halves 
lie very close together, the split is distinct throughout the length 
of each chromosome. I agree with Sharp (’13) that the appear¬ 
ance of free ends of the threads in thick sections may be taken 
to indicate that no continuous spirem is formed. I do not find 
the fine lateral anastomoses described by Sharp (‘13) for Vicia and 
by him ( ’20b) for Tradescantia at this stage, except in cases which 
I do not regard as normal. 
The chromosomes continue to shorten and thicken and assume 
various shapes and positions in the nuclear cavity as shown in 
figure 20. In general the chromosomes lie about the periphery 
of the nucleus as shown in this figure, but as they are compara¬ 
tively long, portions often extend into the center of the cavity. 
The longitudinal split in each chromosome at this period is distinct, 
each chromosome shows a double row of chromatic granules or 
chromomeres. As the chromosomes shorten and thicken still 
more, these chromomeres become still more distinct (fig. 21), 
which distinction is maintained in the chromosomes of the equa¬ 
torial plate as shown in figure 1. Even though the achromatic por¬ 
tions of the chromosomes may unite more or less closely, it is 
evident that the chromomeres remain distinct. Sharp (T3) be¬ 
lieves that although the halves of the chromosomes of Yicia may 
lie very close together they do not fuse. My results in the main 
support this view. It is evident from the two chromosomes ly¬ 
ing in the upper part of the nucleus shown in figure 20 that the 
homologous chromosomes exist in pairs. 
I have not studied the formation of the spindle in detail. The 
phenomena observed in Podophyllum appear to be similar to 
those described for spindle formation in somatic divisions. That 
the formation of the spindle is preceded by the appearance of 
nuclear caps as described by Densmore (’08) for Smilacina and 
by Sharp (’13) for Vicia,, is evident from figure 20. I have ob¬ 
served a rapid contraction of the nucleus at this stage, as pointed 
out for Smilacina and other plants by Lawson (’ll) and by Sharp 
(’13) for Vicia. I agree with Sharp (’13) that the fact that the 
fibres are differentiated in two opposite regions before the nucleus 
begins to contract does not support Lawson’s view of the origin 
of the spindle. 
