LEGUMINOUS CROPS. 



28 



Fig. 6 b). These spores germinate wheii provided with 

 moisture and a suitable medium, and ultimately give rise 

 to conidiophores. The spores of the clover mildew, like 

 those of every fungus, consist of living protoplasm 

 surrounded by a cellulose covering. Near the end of the 

 season, true sexual organs (analogous to the carpels and 

 stamens of the higher plants) are produced from certain 

 hyphse within the leaves of the host-plant (Fig. 6 C, d). 



Fig. 6. — Clotee Mildew (Peronospora trifoUorum). 

 One of the causes of " clover siokness," x about 200. 



The largest of these organs (Fig. 6 C) is the oogonium, or 

 egg-cell; and the smallest (D') is the antheridium, or male 

 cell. The former contains an oosphere. After the anthe- 

 ridium and oogonium have been in contact, and their 

 contents thoroughly commingled, the antheridium dies 

 away ; but the oogonium increases in size and becomes 

 an oospore or restiag-spore. The oospores fall to the 



