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XXXV. 



ON THE ROTTING OF POTATO TUBERS BY A NEW SPECIES 

 OP PHTTOPHTHORA HAVING A METHOD OF SEXUAL 

 REPRODUCTION HITHERTO UNDESCRIBED. 



By GEORGE H. PETHTBRIDGE, Ph.D., B. Sc, 



Economic Botanist to the Department of Agriculture and Technical 

 Instruction for Ireland. 



Plates XLII-XLIV. 



[Eead February 25. Publislied March 26, 1913.] 

 CONTENTS. 



That potato tubers are peculiarly subject to various kinds of decay is a 

 familiar fact. The causes underlying the various forms of rotting are 

 gradually becoming elucidated, but the disentanglement of these causes is no 

 easy matter. For, since the tuber is a structure rich in food, when once it has 

 become killed, or partially so, it forms a substratum on which, as a rule, a 

 most varied micro-flora (and -fauna) develops, which renders the task of ascer- 

 taining the primary cause of the decay in any given instance a difBcult 

 undertaking, and particularly so when the rot has been in progress for some 

 little time. 



It is, of course, possible, and perhaps even probable (although up to the 

 present not much consideration has been given to this side of the question), 

 that potato tubers sometimes die what may be called a natural death, or at 

 least one in which the active participation of parasitic organisms does not 

 occur. Thus, when tubers are stored under improper conditions, it is possible 

 that death may be due to suffocation (owing to lack of oxygen) or to exposure 



SaiENT, PROC. E.D.S., VOL. XIII., NO. SXXV. 4 K 



