86 



STATE HORTICULTURAL SOCIETY. 



Among the higher forms there are a vast number of fungi known as 

 mildews, and from their appearance these are divided into "powdery" and 

 "downy" forms: 



Downy Mildew of the Geape. Peronospora viticola. 



1. Section of leaf (greatly magnified) showing conidieil stage. 



2. Showing the same, less magnified. 



8. The same, showing the effect of the fongns, the leaf brown and shrivelled. 

 4. Germinating conidia. 



5-8. Development of conidia through zoospore and swarm-spore stages. 



9. Spore. 



10. Germinating spore. 



11-13. Fertilization of organiam and development of the oospore. 



14. Section of leaf greatly magnified, showing mycelial thread passing between the 

 cells, and sending its haustoria into them. 



15. Branching mycelium, the spots representing haustoria. —After Viala. 



DOWNY MILDEWS {Peronosporece) , FIG. 3. 



The plants of this group live as parasites in the interior of other plants, 

 and, without entering the cells themselves, they work their way between 

 them, and penetrating the cell walls with their haustoria, or root-like 

 appendages, they drain the cells of their substance and cause them to 

 become brown, and finally dry. 



The mycelium, or plant body of the fungus, consists of long branching 

 filaments which ramify through the substance of their host, and, having 



