59 
Pollen Mother-cells of Certain Plants. 
Fig. 23. Multipolar spindle stage, showing position and form of several chromosomes. 
Fig. 24. Spindle becoming bipolar. Chromosomes appear as short double rods. 
Fig. 25. Equatorial plate stage. Chromosomes mostly in metaphase. Chromosomes shown 
as double V’s. 
Fig. 26. Equatorial plate stage. Chromosomes in late metaphase and in early anaphase. 
Fig. 27. Bivalent chromosomes in various stages of division : 27 a. Side view of early meta- 
phase ; parts separating from within outward. 27 b. Late metaphase showing the double V-shaped 
figure. 27 c. Late metaphase, showing the position of the chromosome when the two halves of each 
univalent portion remain closely applied to each other. 
Fig. 28. Spindle with chromosomes in late anaphase. Each chromosome shows a longitudinal 
splitting. 
Fig. 29. Single chromosome in anaphase ; each chromosome showing longitudinal splitting as 
it diverges toward the pole. 
Fig. 30. Telophase of first division. Chromosomes still distinct but becoming arranged into 
a pseudospirem. 
Fig. 31. Daughter nuclei formed. Pseudospirem present in each nucleus. 
Fig. 32. Polar view of daughter nucleus showing pseudospirem. 
Fig. 33. Equatorial plate stage of second division. 
Fig. 34. Anaphase of second division. 
Fig. 35. Pollen mother-cell with four granddaughter nuclei. 
Fig. 36. Nucleus of young tetrad, showing arrangement of chromosomes into a single series 
with linin intervals. 
Fig. 37. Young pollen grain showing prochromosomes in single series with linin intervals. 
PLATE II. 
Calycanthus Jloridus. 
Fig. 1. Young pollen mother-cell, showing prochromosomes, linin intervals and linin framework. 
Fig. 2. Young pollen mother-cell, showing chromatin not entirely massed in prochromosomes 
but somewhat spread out along linin intervals. 
Fig. 3. Very early synaptic contraction, showing two distinct heterogeneous pre-synaptic 
spirems. 
Fig. 4. Synaptic contraction somewhat more advanced with nucleole in the centre of the mass. 
Fig. 5. Complete synaptic contraction showing the prochromosomes in pairs. 
Fig. 6. Late synaptic contraction. Loops of the bivalent spirem begin to extend into the 
nuclear cavity. 
Fig. 7. Post-synaptic distributed bivalent heterogeneous spirem in which chromosomes are 
visible. 
Fig. 8. Post-synaptic spirem, showing distinct bivalency. Chromosomes and linin intervals are 
distinctly paired. 
Fig. 9. Pairs of single prochromosomes drawn before and during synapsis, showing various 
forms and sizes : 9 a. Prochromosomes composed of granules embedded in linin. 9 b. Two com- 
ponents of a pair very closely associated. 9 c. No trace of granules. 9 d. Apparently similar 
groups of granules in the two components lying opposite each other. 9 e. Prochromosome pair in 
early synapsis, linin and chromatin somewhat contracted. 9/, gg. Prochromosome parts from 
late synapsis. Chromatic substance much condensed. 
Fig. 10. Late diakinesis stage, showing chromosomes much scattered in nuclear cavity. 
Fig. n. Chromosomes from early and late diakinesis, showing various forms: 11 a. Univalent 
portions closely applied and twisted about each other. 1 1 b. The two portions forming an 8-shaped 
figure. 11 c. The two portions forming an O-shaped figure. 1 1 d. The two portions placed endwise, 
also showing indication of longitudinal splitting. 11 e. Characteristic parallel double rods. Longi- 
tudinal split visible in portion at left of figure. 
Fig. 12. Polar view of equatorial plate, nearly all chromosomes seen from end, showing four 
parts. One chromosome much larger than others. 
Fig. 1 3. Side view of spindle. Chromosomes in late metaphase. 
