i 9 o8] BURL1NGAME—PODOCARPUS 177 



Fig. 5. — Detail of sporangium of same age as preceding, showing relations 

 of wall, tapetum (t), and sporogenous tissue (sp). 



Fig. 6. — Cross-section through sporangia; vb, vascular bundle. 



Fig. 7. — Cell of the sporogenous tissue about one division short of the 

 mother cell stage. 



Fig. 6. — Detail of a nucleus a little later than preceding, showing the nuclear 

 materials beginning to arrange themselves into threads with here and there deeply 

 staining chromatin knots. 



Fig. 9. — Surface view of a still older nucleus showing the strands more dis- 

 tinct and larger. 



Fig. 10. — The definitely organized spirem with unusually distinct chromatic 

 knots; the spirem is usually more homogeneous and stains more evenly. 



Fig. 11. — A very thin section of a nucleus whose spirem is beginning to seg- 

 ment into chromosomes; compared with^g. 7, it shows the variation in size and 

 shape of the sporogenous cells. 



Fig. 12. — Longitudinal section of a cell in telophase showing about half of 

 each group of chromosomes; the spindle is curved with the concavity toward the 

 observer. 



Fig. 13. — Showing the reconstruction of the daughter nuclei. 



Fig. 14. — Mother cell showing the emergence of the chromosomes from the 

 granular mass out of which the spindle arises; the granular materials are actually 

 much denser than shown in this figure and nearly conceal the chromosomes. 



Fig. 15. — Longitudinal section of the heterotypic spindle. 



Fig. 16. — Late anaphase of the heterotypic mitosis. 



Fig. 17. — The homotypic mitosis. 



PLA TE IX 



(Figs. 18-27, 33 are P. totarra Hallii; figs. 28-32 are P. nivalis) 



Fig. 18. — Section of microspore slightly oblique to the wings; i, intine; e, 

 exine. 



Fig. 19. — Male gametophyte showing first prothallial cell (/»,) divided, no 

 second prothallial (p 2 ) cell, primary spermatogenous cell (ps), and in next section 

 the tube nucleus (t). 



Fig. 20. — Same stage as preceding except that there are here two primary 

 prothallial cells (p 2 ), the second of which has divided (only one, p 2 , of the seg- 

 ments shown). 



Fig. 21. — Same as fig. 19 except that the single primary prothallial cell (p t ) 

 has not divided; /, tube nucleus. 



Fig. 22. — Male gametophyte showing first prothallial (p x ) undivided, second 

 (p) 2 divided once, primary spermatogenous cell (ps), and tube nucleus (t). 



Fig. 23. — Same as preceding except that first prothallial cell (p) has also 

 divided and the primary spermatogenous cell (ps) has sunk down between the 

 derivatives of the second prothallial cell (p 2 ); adjacent sections show that there 

 are here four derivatives of the second prothallial cell. 



