104 PLANT-LIFE 



method whereby a plant, originally aquatic, may be- 

 come adapted to land conditions. 



But we have not noted the greatest triumph of this 

 ingenious Fungus. It must necessarily come up against 

 such a degree of drought as will make active growth 

 impossible, and, in order to maintain the species through 

 the adverse season, it produces sexual resting-spores. 

 The sexual organs occur on aerial hyphae and also on 

 hyphsD growing within the host plant. The oogonia 

 (female organs) occur as enlarged spheres at the ends 



of hyphae, or at intermediate 

 points. The male organs (an- 

 theridia) are club-shaped; they 

 may appear on the same or 

 separate filaments. The ferti- 

 le 34.-THE FEBTILIZATION lizin g P rOC6SS is ^strated in 

 OF PYTHIUM. x 800. Fig. 34. An antheridium reaches 



A, Immature oogonium (o), and out to the nearest OOgOnium 



5S ( t and p enetrates * with a ferti - 



passing from antheridium lizing tube; the contents of the 



(a) through the tube to the mftle ng through the 



ovum (o). . * r . ! 



tube into the oogonium and 



fertilize the ovum contained therein. Spermatozoids are 

 not formed. The fertilized ovum secretes a stout mem- 

 brane about itself, develops a store of oil, and enters 

 upon a period of rest, during which it can resist 

 drought and cold, and may be borne a long distance 

 by wind. The resting-spore can germinate only in 

 water, and, in germinating, may behave in three ways : 

 it may produce hyphae and the usual mycelium forth- 

 with; it may give rise to a hypha which, instead of 

 forming a mycelium, forms a sporangium and zoospores, 



