92 



FUNGOID DISEASES 



Precatitions. — 



1. Examine sets carefully prior to planting, and 

 reject all with blotches. 



2. Do not plant potatoes immediately after 

 limino-. 



3. Shun those varieties which are most sus- 

 ceptible to the attack — *' Evergood," "Flourball," 

 etc. 



4. Examine " Evergood " seed carefully, and 

 reject any " blind " sets. 



Fig. 25. — {Spicaria nivca) : (A) microscopic section through one of the 

 pimples on the potato showing the fungus mycelium (;;/) inside the 

 cells ; (c) the ctll wall ; (/') the remains of digested starch giains ; (B) 

 portion of the hyphae of Spicaria nivea showing the formation of the 

 spores in chains. (Highly magnified.) 



{/)) Black irregular markings, — Caused by Rhiz- 

 octonia. Here the skin is perfectly intact and the 

 blackness can be rubbed or washed off. 



[c) Some scu7'f diseases, not of a serious nature, 

 are said to be due to mechanical disturbances. 



(rtf) The lenticels are often seen in the form of small 



