DAMPING OFF 



55 



of rest before germination takes place. The sporangia 

 possess a single tubelike projection into which the proto- 

 plasm passes and forms a sphere at its tip, which breaks 

 up into biciliate zoospores. 



Fig. 4. — Pythium de baryanmn. i, seedlings of cress {Lepidinm 

 sativum) attacked by the fungus ; 2, mycelium bearing conidia at the 

 tips of the branches, X 300; 3, sporangia in different stages, also a free 

 zoospore, x 300; 4, an oosphere, with the antheridium or male organ, 

 which has pierced the wall of the oosphere and inserted a slender tube, 

 for the purpose of allowing the contents of the antheridium to mingle 

 with those of the oosphere. After this blending of the contents of the two 

 organs, the oosphere becomes enclosed in a thick wall, to form the 

 oospore or sexually produced resting-spore, x 300 ; 5, a germinating 

 conidium, x 300. 



Both oospores and resting conidia remain on the ground 

 and produce zoospores after a period of hibernation. 



