Nov., 1914.] Stamens of Smilax herbacea. 367 



Explanation of Plates XVI and XVII. 



The plates were reduced f in reproduction. All the drawings 

 were made with a compensating ocular 12 and a 1-lG oil immersion 

 lens. An Abbe camera lucida was used. 



Fig. 1. Microsporocyte before the beginning of the division of the chro- 

 matin network. 



Fig. 2. Microsporocyte showing tlie flaky and spongy appearance of the 

 chromatin material. 



Fig. 3. Masses of chromatin material which are the protochromosomes. 



Figs 4, 5. Later stages showing the elongation of the protochromosomes 

 in their tendency to form a spirem by stretching out along the 

 linin thread. 



Fig. 6. Early spirem with irregular flakes along its sides. 



Fig. 7. Early spirem with small granules. 



Fig. 8. Microsporocytes showing the spirem free from the nuclear mem- 

 brane and collapsing. 



Figs. 9, 10. Sporocytes showing different types of synizesis. 



Fig. 11. Sporocyte in synizesis with the projecting strands showing granules. 



Fig. 12. A synizetic knot with rather heavy projecting loops. 



Fig. 13. Heavy spirem showing granules and beginning of looping. 



Fig. 14. Sporocyte showing the double nature of the spirem and granules. 



Fig. 15. Sporocyte showing the early looping stage and double spirem. 



Fig. 16. Sporocyte showing well formed loops. 



Fig. 17. Chromatin loops completely formed and just breaking apart. 



Figs. 18, 19, 20. Sporocytes showing the prominent chromosomes that 

 have not completely separated, but still show some connecting 

 threads. 



Figs. 21, 22, 23. Sporocytes showing the twelve mature chromosomes; 

 the looped nature of the chromosomes is still evident in most 

 cases. 



Fig. 24. Sporocyte showing the delicate connections between the chro- 

 mosomes and the incipient spindle. 



Fig. 25. Chromosomes in the spindle being drawn into the equatorial 

 plane. 



Fig. 26. Early stage of metakinesis showing the chromosomes dividing. 



Fig. 27. Later stage of metakinesis showing most of the chromosomes 

 divided. ^ . 



Fig. 28. Daughter star of the first division. 



Fig. 29. Daughter cells showing the more or less distinct chromatin masses 

 in the nuclei. 



Fig. 30. Mother star of the second division. 



Fig. 31. Daughter star of the second division. 



Fig. 32. Polar view of the twelve chromosomes of a daughter star of the 

 second division. 



Fig. 33. Normal tetrad within the old sporocyte wall still showing the 

 more or less distinct daughter chromosomes. 



