PLATE IV 
Phytopklhora infestans: Infection of potato tubers 
Fig. i.—Cross section of a tuber which was infected with P. infestans and was planted 
in the greenhouse in rather dry soil. After two months it was dug up and found to 
be firm and containing living mycelium of the fungus. 
Fig. 2.—This tuber was inoculated at the eye surrounded by the paraffin ring. The 
mycelium ran through the tissues and grew out into four of the sprouts at the bud end of 
the tuber. 
Fig. 3.—Cross section of an infected tuber planted in sterilized soil in the green¬ 
house which developed a shoot that became infected through the parent tuber. 
Fig. 4.—The small stunted shoot which grew from this infected tuber shows the pro¬ 
gressive discoloration caused by P. infestans growing up the stem. 
