34 PRESENT DISEASE IN THE POTATOE. 



cur between these necessary constituents of the organic 

 body. 



(129.) Sometimes the potatoe tops lose their leaves with 

 the exception of a few at the extreme top, which will re- 

 main and help to nourish the plant ; at other times they 

 totally rot, and the mere remains are to be seen in the 

 field. In the first case, the plant has been more mature 

 when the disease appeared ; in the second, the stem has 

 been more succulent. The potatoes or tubers of a plant 

 are not all necessarily destroyed : some will be immature 

 and will not keep, others will be thoroughly rotten, and 

 some will be but slightly injured ; and, as a general rule, 

 tubers in all states are found on every diseased plant. 



(130.) The tuber suffers less, or, I may state generally, 

 all the plant suffers less, the older it is before it manifests 

 the disease, because the death of any part of the plant 

 necessarily cuts off nourishment from the rest. 



(131.) It is remarkable that even those tubers of diseased 

 plants which appear sound in the first instance, are very 

 apt to become diseased upon keeping ; and whole cargoes 

 of potatoes, which, when shipped, are to all appearance 

 perfectly good, prove only fit for manure when they reach 

 their destination. 



(132.) Thus we may infer that every part of a diseased 

 plant is diseased. As a consequence of the individuality 

 of a plant being preserved and propagated from parent to 

 offspring, a plant originally diseased will continue its dis- 

 ease in any new growth which originates from it. And 

 thus it is impossible to tell for how long the disease may 

 continue to show itself in the progeny of a plant once in- 

 fected. The probability is, that in time, if the original 



