172 BOTANICAL GAZETTE [march 



PLATE VI 



Mitosis in the vegetative cells of the prothallium 



Fig. i. Prophase; nucleus with a continuous spirem. 



Fig. 2. The nucleus after segmentation of spirem into a number of chromo- 

 somes, most of them before the stage of longitudinal splitting; two kinoplasmic 

 caps with a few fibers are present. 



Fig. 3. The nucleus after disappearance of membrane; chromosomes which 

 are split longitudinally show a tendency to become arranged parallel to the axis 

 passing between the two poles. 



Fig. 4. Late prophase; daughter halves of chromosomes are in close contact 

 with each other; they have shortened to L forms and are regularly arranged in 

 an equatorial plate; the vertical arms of the L's are directed to the poles, while 

 the horizontal arms are lying in the plate. 



Fig. 5. Polar view of the stage shown in fig. 4; the horizontal arms of the 

 L's are in regularly radiating arrangement and the optical section of the vertical 

 arms appear like dots. 



Fig. 6. Early anaphase; daughter chromosomes separating in a group. 



Fig. 7. Late anaphase; two sets of daughter chromosomes near the pole. 



Fig. 8. Early telophase; daughter chromosomes regularly arranged at poles. 



Fig. 9. Polar view of the stage shown in the previous figure; 64 chromosomes 

 present. 



Fig. 10. Telophase; two daughter nuclei and a cell plate formed; arrange- 

 ment of chromatin substance in daughter nuclei showing polarity. 



Spermatogenesis 



Fig. 11. Telophase preceding formation of spermatid mother cells; nuclei of 

 spermatid mother cells just organized; two nucleoli present in one of the nuclei. 



Fig. 12. Condition of nucleus later than stage shown in fig. 11; chromatin 

 material very scanty in polar region, where nucleoli are present. 



Fig. 13. Still later stage than that in fig. 12; arrangement of chromatin material 

 still showing polarity. 



Fig. 14. More advanced stage than that shown in fig. 13 ; nucleus of sper- 

 matid mother cell almost in resting stage; no polarity in distribution of chromatin 

 material; two blepharoplasts within cytoplasm on opposite sides of nucleus. 



Fig. 15. Nucleus of spermatid mother cell with spirem; two kinoplasmic 

 caps with a few fibers; blepharoplast near pole of fibers. 



Fig. 16. Spirem segmented into chromosomes; nuclear membrane begins 

 to disappear at poles of nucleus; blepharoplast near the pole. 



Fig. 17. Late prophase; nuclear membrane has completely disappeared; 

 chromosomes split longitudinally; blepharoplast near center of spindle. 



Fig. 18. Anaphase; two sets of daughter chromosomes on the way toward 

 the poles. 



Fig. 19. Early telophase ; daughter chromosomes grouped at pole with regular 

 arrangement; blepharoplast retains same position as before. 



