22 DISEASES OF TROPICAL PLANTS CH. 



and much less conspicuous. The yeast plants are not 

 filamentous but each plant is a single, very minute, 

 roundish cell. Some fungi are so small that they live 

 in a single cell of a higher plant. 



Saprophytes. - - The saprophytic fungi are those 



which live upon dead or- 

 ganic material, such as 

 bread, decaying fruit, and 

 vegetables, wood, meats, 

 leather, horn, dung, etc. 

 The decay of these various 

 substances is due partially 

 to the action of the fungus 

 and partially to the action 



FK;. 11. Sweet potato affected with wet rot, 

 due to R/iizopus nigricans. (Photograph 

 by .1. J. Taubenhaus. ) 



Fi<;. 12. Rhiznpns niyricans, showing 

 sporangia. 



of bacteria and other organisms which are so often 

 associated with them. 



Parasites. The parasitic fungi are those which live 

 on living plants or animals ; the number which live 



