PLATE 37 



Photographs enlarged from portions of a motion photomicrograph, showing the 

 method of cell wall penetration by Pythium hyphae. 



A. — Shows the hypha growing against the potato cell wall. Sufficient pressure has 

 already been applied to cause the hypha to bend. Notice that this bending increases 

 in later photographs. 



B. — ^A little later stage than A. 



C. — The tip has broken through as a small tube . 



D. — Penetration is complete. Notice the constriction of the hypha at the point 

 where it?.penetrates the potato cell wall. 



