228 PHYTOPHTHORA PARASITICA. 



Fig. 6. A germ-tube entering a castor leaf by breaking through the upper wal] 

 of its epidermal cell. X 405. 

 ,, 7. A germ-tube entering a castor leaf between the Avails ot two con- 

 tiguous epidermal cells. X 405. 



Figs. 8 — 11. Surface views of castor leaves showing the three ways in which the 

 germ-tube enters the leaf. In Fig. 10 the germ-tube crosses over a 

 stoma before entering the leaf. X 405. 



PLATE IV. 



Fig. 1. Papilla swelling into a vesicle in which the sporangium is discharging 



mature zoospores. (Fixed with iodine.) X 405. 

 „ 2. An advanced stage of the same. (Fixed with iodine.) X 405. 

 i} 3. The vesicle has dissolved; the zoospores are still clumped together. 



(Fixed with iodine.) X 405. 

 ,, 4. The papilla has dissolved but the zoosjiores are still within the 



sporangium. X 405. 

 j, 5. The discharge of zoospores in the normal way. The zoospore that is 



just out of the sporangium is linked to the one immediately behind 



it by a protoplasmic neck. X 640. 

 „ 6. Zoospores. A shows two zoospores Jinked together by a protoplasmic 



neck and possessing two cilia. X 640. 

 ,, 7. A zoospore which came to rest at 10-20. X 640. 

 Figs. 8 — 24. .Successive stages in its germination. Fig. 8 drawn at 10-35. Figs. 'J to 



14 drawn at intervals of five minutes. Figs. 15 to 24 drawn at 1 1-40, 



11-45, 12, 12-35, 12-45, 1-20, 1-40, 2, 2-25 and 3-15 respectively. 



X640. 

 Fig. 25. Germination of zoospores by two germ-tubes. X 640. 



,, 26. A motile mass of protoplasm with rive visible cilia. (Freehand drawing.) 

 „ 27. The same in its resting stage. Drawn at 10-30. X 405. 

 Figs. 28 — 34. Successive stages of its germination. Observe the gradual dis- 

 appearance of the outer wall. These figures were drawn at 10-45. 



10-55, 11-5, 11-25. 12-10, 1 and 3 respectively. X 405. 

 Fig. 35. A sporangium germinating into a secondary sporangium. X 405. 

 ,, 36. A bi-papillate sporangium. X 405. 

 „ 37. A sporangium producing in water cultures secondary and tertiary 



sporangia when kept under normal conditions for twenty-four 



hours. X 100. 



PLATE V. 



Fig. 1. Typical aerial mycelium growing on French-bean juice agar and oat 

 juice agar. ('/) A " resting ; " conidium. (b) an intercalar sporangium. 

 At (x) are cellulose deposits on the inner walls of the hypha. They 

 have partially closed the hypha. The lowermost sporangium also 

 shows a cellulose deposit on its inner wall and just above its point 

 of attachment to the sporangiophore. X 405. 



