140 Arlow Burdette Stout, The individuality of the chromosomes, etc. 
Fig. 22. Synapsis. 
Fig. 23. PachjTieme stage of post-synapsis. 
Fig. 24. DiaJiinesis. Chromosomes in pairs at the periphery. Spirem some- 
what in evidence. 
Fig. 25. Stage following diakinesis. Bivalent spirem drawing in from the peri- 
phery. Lower part of the nucleus in cell a not shown. 
Fig. 26. A Stage somewhat later than the one showm in fig. 25. Spirem is more 
toward the center of the nucleus. The bivalent chromosomes appear more compact. 
Fig. 27. Polar view of the equatorial plate of the heterotypic division: 37 pairs 
of chromosomes in view; most of them in profile. The serial arrangement can be traced 
for some distance. 
Fig. 28. Lateral view of the equatorial plate of the heterot 3 "pic division just 
previous to the Separation of the paired chromosomes. 
Fig. 29. Telophase of the heterotypic division. 
Fig. 39. Homoeotvpic divisions; both polar and lateral views shown. 
Fig. 31. Cell showing the four microspore nuclei. Only the large central one 
will develop ; the three at the apex will eventually disintegrate. All show the chro- 
mosomes. 
Fig. 32. Stage showing the elongated generative cell. The vegetative nucleus 
lies at a lower level and is only shown in part. 
Fig. 33. Median section through a pollen grain showing vegetative nucleus, 
generative cell which is now rounded, and two of the cells at the apex. Chromosomes 
are present in all the nuclei and the serial arrangement is in evidence. 
Fig. 34. Portion of a pollen grain showing generative cell in prophase. The 
spirem consists of individual chromosomes. 
Fig. 35. Showing telophase in the division of the generative cell. At the apex 
of the grain is shown a portion of the plate formed by the disintegrating nuclei. 
Fig. 36. Portion of a mature pollen grain showing nucleus of the vegetative cell 
and the two germ cells. The chromosomes are visible in all three nuclei. 
