No. 216.] 603 



6th. The circumstances of soil, climate, cultivntioTi, &c., will da 

 much to vary the apparent loss of vitality from age in plants. 



7th. Plants that hai,e lost their vitality are more subject to the at- 

 tack of parasites than plants in a vigorous state. Plants have their 

 peculiar parasites but they are not always confined in their depreda- 

 tions to the plants in which they originate. 



8th. The production of abundant blossoms, few of which are sue- 

 ceeded by mature fruit, is an indication of loss of vitality, and gen- 

 erally on account of old age. 



These propositions are too simple, and obvious to every careful ob- 

 server, to admit any doubt. It would indeed, seem to be a retrograde 

 movement in science to attempt to prove them, yet if granted, they 

 are sufficient for my purpose; they will explain all the phenomena 

 that have been observed and reported in relation to the potato rot. 



The plant is said to be attacked by aphides ; this is true, but it is 

 explained by the 7th proposition abov-e. Plants that have lost their 

 vitality are more subject to the attacks of parasites than plants in full 

 vigor. Fungi have been found in great abundance upon the diseased 

 plants. This is explained in the same way, but it is said the attacks 

 of these same fungi are not confined to the potato, and hence it is in- 

 ferred that they do not originate in a disease peculiar to this plant. 

 Parasites often prey upon plants in which they never originate. 



It is said again, that crops, in many instances, were less injured 

 by the rot in 1846, than crops upon the same ground were in 1845; 

 although the seed for the crop of 1846 was taken from the crop of 

 1845. This is explained by the 6th proposition, which also accounts 

 for the different degrees of disease in different soils and with differ- 

 ent manures. In short there is no well authenticated fact in relation 

 to the disease, that may not be satisfiictorily explained by supposing 

 the cause to be too long continued propagation from by the root, 

 without renewing from the seed. 



Although I have already said more than I at first intended to say^ 

 yet I cannot dismiss the subject without bestowing a hasty notice 

 opon some editorial remarks in the Cultivator. 



I regret that a person who stands so high, as does the editor of 

 this valuable periodical, allows himself to take so superficial views of 

 this important subject. In an article in the January No., p. 21, be 



