146 Wager —On Peronospora parasitica. 
Fig. 12. Another section of the oogonium shown in Fig. 11, showing a second 
nucleus in the protoplasm of the oosphere. Letters as in Fig. 11. In this section 
the antheridial tube is not visible, x about 800, Swift’s ^ water-immersion. 
Fig. 13. Section of an oogonium with the antheridial tube in connection with 
the oosphere. The antheridial tube contains a single nucleus, n . The wall of the 
oosphere, 0, is now distinctly seen, x 1000. 
Fig. 14. Section of an oogonium and antheridium just before fertilisation takes 
place. The antheridial tube, a', contains one nucleus, n , near the end of its swollen 
part. The oosphere contains a single nucleus, rC . x 1000. 
Fig. 15. Section of an oogonium after fertilisation is supposed to have taken 
place. The antheridial tube is seen to open into the oosphere by a small hole, f 
placed very near the end of its swollen portion. The antheridium contains a 
number of nuclei, and the oospore, 0, contains two very faintly stained nuclei, n. 
x 1000. 
Fig. 16. Section of an oogonium with its antheridium, a, showing the antheri- 
dial tube, a\ much contracted, x 1000. 
Fig. 17. Section of an oogonium, with its antheridium, a , in a much later stage. 
The wall of the oogonium, og , is much contracted, and the antheridium and tube, 
a', are becoming disorganised, the former still containing a number of nuclei, w!'. 
x 1000. 
Fig. 18. Section of an oogonium in a much later stage. Two nuclei, n , are still 
to be seen in the oospore, 0, the periplasm, /, has become less granular and is 
more hyaline, and is gradually forming a dense compact layer on the wall of the 
oospore, the periplasmic nuclei at the same time becoming disorganised, x 1 000. 
Fig. 19. Section of a gonidium of P. parasitica showing numerous nuclei the 
structure of which is different from the nuclei of the mycelium and oogonium ; h, 
slighlty stained nucleoplasm surrounding a central mass of chromatin, c. x 1000. 
