Pollen Mother-cells of Certain Plants. 29 
nucleus (Fig. 29, PI. I). They also remain distinctly separated even after 
the formation of the nuclear membrane (Fig. 30, PL I). In Fig. 30, PI. I, 
the daughter nucleus to the right of the figure shows the short two-parted 
chromosomes becoming arranged into a sort of spirem. The chromosomes 
are united by linin fibres into a single series. This condition shows dis- 
tinctly in Figs. 31 and 32, PL I. In Fig. 32, PL I, which is a polar view 
of a daughter nucleus, I was also able to trace a continuous linin spirem. in 
which the chromosomes are arranged at rather regular intervals. These 
stages show that the chromosomes of the daughter nuclei become arranged 
into a linear series during the reconstruction stages. This spirem, however, 
is not a continuous chromatic spirem, but is heterogeneous, composed of 
chromosomes with intervals of linin as has been described for the prophases 
of the heterotypic nuclei. Each chromosome remains distinct. They may 
even be counted here, as they never are lost to view by a process of reticula- 
tion or alveolization. Although the chromosomes may be identified in the 
resting daughter nuclei, their small size renders them unfavourable for a 
very detailed study of their structure, but they often become somewhat 
distributed along the linin as in the prophases of the first division. In this 
spirem each chromosome manifests the split which occurred in the pro- 
phases of the first division (Figs. 30 and 31, PL I). Each chromosome 
remains, therefore, two-parted in the spirem. 
The daughter nuclei increase in size and the phenomena characteristic 
of this division apparently follow each other, in rapid succession. The 
chromosomes appear in the same relative position and form in which they 
entered the nuclei. The segmentation of the heterogeneous spirem is the 
same as in the prophases of the first division. If the chromosomes are 
at all distributed they become condensed, losing what alveolar-reticulate 
structure they possess, and again appear as homogeneous bodies. Each 
chromosome, however, may be seen to be composed of two segments as in 
the preceding telophase (Fig. 32, PL I). As the nuclear membrane dis- 
appears the spindle fibres become attached to the chromosomes, arranging 
them in the equatorial plate (Fig. 33, Pl. I). The spindle fibres are attached 
at one end of the chromosomes separating the halves much as in most 
vegetative divisions (Fig. 34, PL I). 
The reconstruction of the granddaughter nuclei is of interest, since 
the segments or chromosomes are visible as prochromosomes even in the 
nucleus of the pollen grain. Fig. 35, PI. I, shows the four nuclei with the 
chromosomes still distinct. Fig. 36, PL I, shows how these univalent 
chromosomes are arranged into a spirem composed of chromosomes and 
linin portions. During the reconstruction of these nuclei the chromosomes 
become arranged into this heterogeneous spirem by means of linin con- 
nexions or intervals. Each chromosome is, however, distinct, nor are the 
chromosomes entirely reticulated or alveolized in these nuclei up to the 
