AGRICULTURAL EXPERIMENT STATION. 173 



Explanation of Plate. 

 This plate was used by Prof. C. H. Fernald, to illustrate an 

 article on the Potato Rot, which appeared in the Agricultural 

 Report of Maine, 1882, p. 210. The plate was kindly loaned by 

 Mr. Gilbert. In using it, we are aware that the occurrence of 

 winter, or oospores is doubted by many botanists. The writer 

 having never seen them is not prepared to advocate either view, 

 though analogy would strongly suggest their existence. The plate 

 represents fairly well the mycelium, conidiophores and conidia. 



1. Section of a potato leaf showing three mycelium threads 

 running between the cells, and two conidiophores extending from 

 them down through a breathing pore (stomate) on the under side 

 of the leaf. One has two lateral branches with conidia at the 

 ends, while on the top of the main stem is borne a conidium from 

 which zoospores are escaping. 



(The figure is wrong in representing the terminal spore as the 

 first to mature. The young conidia are formed at the ends of the 

 branches. The lateral are the first to mature.) 



2. Conidium showing swarming spores within. 



3. A zoospore much enlarged and provided with cilia. 



4. 5 and 6. Represent winter spores (oospores) claimed to 

 have been seen by Mr. W. G. Smith, but doubted by most 

 botanists. 



7. Three zoospores swimming through water. 



8. Three zoospores becoming spherical and losing the cilia. 



9 and 10. The zoospores germinating and producing mycelium. 



