Davis —Cytological Studies on Oenothera. /. 571 
Fig. 40. Late anaphase, chromosomes gathering at the poles of the spindle. 
Fig. 41. A group of chromosomes in late anaphase of the heterotypic mitosis (cut obliquely), 
showing certain of the chromosomes split lengthwise. 
Fig. 42. Group of seven split chromosomes gathered at the pole of the heterotypic spindle 
viewed from above. 
Fig. 43. Telophase of the heterotypic mitosis, the halves of the split chromosomes bending 
away from one another, showing a tendency to branch and to form an open network, small nucleoli 
appearing. 
Fig. 44. The resting nucleus of the interkinesis between the heterotypic and homotypic mitoses. 
Seven split chromosomes are present, the halves in the form of U’s joined together in the bent middle 
region. 
Fig. 45. Pollen mother-cell containing resting nuclei in the interkinesis following the heterotypic 
mitosis, seven split chromosomes evident in the lower nucleus of the two. 
Fig. 46. Prophase of spindle formation of the homotypic mitosis, the seven split chromosomes 
distributed throughout the nuclear cavity surrounded by a web of fibrillae. 
Figs. 4 7 and 48. Multipolar stages in the formation of the spindle, the split chromosomes 
being gathered at the equatorial plate. 
Fig. 49. Metaphase of the homotypic mitosis, split chromosomes at the equatorial plate. 
Fig. 50. The separation of the halves of the split chromosomes. 
Fig. 51. Anaphase of the homotypic mitosis, showing certain irregularities in the forms of the 
chromosomes. 
Fig. 52. Anaphase, the two groups of chromosomes, seven in each. 
Fig. 53. Late anaphase of the homotypic mitosis, the upper group of seven chromosomes viewed 
from the pole of the spindle. 
Fig* 54 * Early telophase following the homotypic mitosis, the chromosomes becoming 
elongated and irregular in outline. 
Eig. 55. Pollen mother-cell shortly before the formation of the pollen tetrad, chromosomes of 
irregular form connected by a very open reticulum. 
Fig. 56. Nucleus of young pollen-grain, chromatic bodies present in an open reticulum. 
