Sexual Organs of Phytophthora erythroseptica , Pethyb . 153 
Fig. 7. The same in transverse section. The incept has grown obliquely through the antheridium 
and is emerging somewhat to one side, (a) The hypha which gave rise to the oogonial incept 
(b) The lower part of the incept with its antheridial sheath within the male organ. (^) The 
emergence of the oogonial incept. 
Fig. 8. Further stage in the emergence of the oogonial incept. 
Figs. 9 and io. Stages in the development of the oogonium after emergence. 
Fig. 11. A transverse section of organs of about the same age as in the last figure. ( a ) A section 
through the lower part of the stalk of the oogonium within the antheridium. ( b) A section through 
the upper part of the stalk within the antheridium. ( c ) A section through the part of the oogonium 
which has emerged from the male organ. 
Figs. 12 and 13. Further stages in the growth of the oogonium after emergence. Fig. 13 
shows evidence of the rapid inward flow of the protoplasm. 
Fig. 14. A transverse section through an antheridium of the same age as that shown in Fig. 13 
with the stalk of the oogonium inside. 
Fig. 15. The degeneration of nuclei in both organs before division. Tangential section. 
Fig. 16. The same. The oogonium is now cut off by a thick plug in the stalk and the 
antheridium is cut off by septa. 
Fig. 17. The arrangement of the nuclei during division. 
Fig. 18. The same during the concluding phases. The nuclei have moved towards the 
periphery. 
Fig. 19. The completion of nuclear division. 
Fig. 20. The formation of the daughter nuclei. The zonation stage is about to set in. 
Fig. 21. A longitudinal section through the sexual organs after nuclear division showing the 
manocyst or receptive papilla. 
Fig. 22. The zonation stage in the oogonium. The functional female nucleus is seen in the 
centre. 
Fig. 23. Another section showing the zonation stage and the degeneration of the peripheral 
nuclei. 
Fig. 24. The formation of the fertilization tube. 
Fig. 25. A longitudinal section through the sexual organs at the time of fertilization. ( a ) The 
fertilization tube containing the male nucleus. ( b ) The next section through the oogonium showing 
the female nucleus. 
Fig. 26. A fertilization tube showing how the cytoplasm of the antheridium follows after the 
male nucleus. 
Fig. 27. The stage just after fertilization, showing the male and female and the remains of the 
peripheral nuclei. The periplasm has disappeared. 
PLATE III. 
Fig. 28. A longitudinal section through the sexual organs after fertilization. The oosphere has 
contracted somewhat, the remains of the fertilization tube are seen, and the antheridium is almost 
empty. 
Fig. 29. A transverse section through an antheridium after fertilization, showing the almost 
empty condition and the presence of the stalk of the oogonium still inside. 
Fig. 30. The formation of the oospore wall. 
Fig. 31. Further stage of the same with the male nucleus in its characteristic position by the 
spore wall. 
Fig. 32. A section through a spore with the wall practically full-grown. The nuclei are now in 
contact. 
Figs. 33 and 34. Sections through mature spores showing the nuclei in the act of fusion. 
Fig. 35. A section showing the outline of the oogonium and antheridium with a mature spore 
containing a fusion nucleus. 
Fig. 36. One perfect nucleus (to right) and four nuclei showing various stages of degeneration, 
from the same oogonium. 
Figs. 37 and 38. Spireme stages. 
Figs. 39-41. The formation of the chromosomes. 
Figs. 42-48. Various stages of metaphase and anaphase. 
Fig. 49. Telophase. 
