230 l'HYTOl'HTllOHA PARASITICA. 



Fig. 12. Ooognium originating within the intercalar antheridium. Optical 

 section. 



,, 13. Oogonium borne on a short stalk, not sessile on the antheridium. 



,, 14. Hvpha bearing the oogonial stalk within the antheridium swelling at its 

 point of entrance. 



„ 15. Oogonium borne on a lateral branch, the point of entrance of the oogo- 

 nial hyphse is clearly visible. The hvpha enters the antheridium from 

 below and leaves it at its apex. The dotted lines indicate the hvpha 

 underneath the antheridium. 



,, 10. Oogonium separated from antheridium which persists enclosing its stalk. 



,, 17. Optical section of an oogonium originating from the base of an anthe- 

 ridium. 



,, 18. Optical section of an oogonium developed from a separate oogonial 

 stalk piercing the antheridium. 

 Figs. 19 and 21. Optical sections, same as Fig. 17. In Fig. 19, there is a cellulose 



plug in the oogonial stalk. 

 Fig. 20. Hvpha bearing oogonial stalk penetrating the antheridium from above. 

 The dotted lines show the stalk within the antheridium. 



,, 22. Same as Fig. 15. 



PLATE VII. 



Fig. 1. Oogonial thread (0) originating within the antheridium (A). X 500. 

 ,, 2. Mature oospore from French-bean juice agar. Oogonium arising within 



the antheridium. X 400. 

 ,, 3. Mature oospore from French-bean juice agar. Hypha bearing the 



oogonial stalk penetrating the antheridium on the left. X 400. 

 ,, 4. A group of mature oosjwres from French-bean juice agar. X 400. 

 „ 5. A mature oospore from French-bean juice agar roughly manipulated. 

 The passage made by the oogonial stalk within the antheridium 

 is clearly visible. X 400. 

 „ G. Oospore from oat juice agar. X 400. 

 „ 7. 0. Oospores from French-bean juice agar, 

 iv. " Resting " conidia. X 400. 

 8. " Resting " conidia. X 400. 



PLATE VIII. 



Fig. A. Seedling of Potato. The central shoot marked with an arrowhead 

 was inoculated. The other two shoots served as controls. Photo 

 taken five days after inoculation. 

 „ B. Seedlings of tomato. On the left is the inoculated seedling ; the other 

 was kept uninoculated as a check. Photo taken three days after 

 inoculation. 



