POTATO DISEASE. 121 



tion to earlier sorts, which, are found to stand the winter quite 

 as well as the later varieties ; but as a rule, good and undiseased 

 sets should be used. At the same time we know from experi- 

 ment that on planting in a fine dry year tubers much diseased, a 

 crop without any signs of the murrain has been secured. 



Since reading Mr. Smith's remarks in various papers we have 

 been careful to instruct the cottagers to burn all the haulm and 

 refuse weeds from a potato-crop ; but above all he would recom- 

 mend the introduction of fresh hardy sorts, or at least a fresh 

 seed. Nothing pays better in this respect than a change of 

 seed ; and although we do not believe in a disease-resisting 

 potato any more than in a measle-resisting animal, yet we feel 

 sure that whatever tends to the health of this crop will afford a 

 means of averting much potato disease even in the worst seasons. 



FUNGI OF POTATO DISEASE. 



The two fungi of the Potato Disease — Poronosfora infestans, 

 Mont., and Fusisporium Solani, Mart., growing in company on 

 the cuticle of fruit of Tomato. 



A, Peronospora infestans with its spores (= acrospores or 

 eonidia), the spores naturally dividing themselves into parts and 

 forming zoospores at A. 



B, Motile flag ellata, zoospores emerging from the spores. 



C, Oogonium, Q^g, or resting-spore of the Peronospora just 

 under the Tomato cuticle, the smaller sub globose body attached 

 to the resting-spore is the antheridium' or male body which by 

 pouring its contents into the resting spore, fertilizes it and 

 makes its nature differ in the same was as a fertile seed differs 

 from an ovule. 



D, Fusisporium Solani with its tri-septate or compound spores. 



E, Compound spore breaking up into four simple spores. 



P, Eesting-spores of the Fusisporitim : these are the simple 

 spores which have become round and slightly echinulate after 

 falling from the pedicels. 



