xxxv.] POTATO DISEASE, I. ITS ACTIVE STATE. 281 



leaves and stems, but also tlie tubers." The following 

 interesting and instructive sentence occurs in an excellent 

 essay written by Dr. W. Peard, LL.B., on "Certain Enemies 

 of our Roots," and published in the Journal of the Bath and 

 West of England Society and Southern Counties Association, 

 vol. iv., third series, p. 14 : "At that time (Aug. 1845) 

 we were spending some weeks at Bally shannon, and close 

 to our cottage was a magnificent field of potatoes, about 

 twenty acres in extent, through which we passed regularly 

 every morning and evening. One day, during the last 

 week in August, as we brushed through the dark-green 

 foliage, earthy disagreeable odours, before unknown to us, 

 rose from the plants. On the following morning the 

 entire crop looked as if it had been exposed during the 

 night to the action of steam. Stems and leaves were 

 soft, pulpy, and blackened ; in six-and-thirty hours a few 

 sickly stems and discoloured leaves were all that remained. 

 The crop had ceased to exist." 



Mr. J. G. Baker, F.R.S., of Kew, is of opinion that the 

 potato plant, Solanum tuber osum, L., in its present " tuber- 

 bearing state is in a disorganised, unhealthy condition, a 

 fitting subject for the attacks of fungi and aphides ;" and 

 he quotes Mr. T. A. Knight to the effect that the formation 

 of the tubers more or less deprives the potato plant of its 

 requisite amount of nutriment. He considers that the 

 potato is grown in a necessarily unnatural way in masses 

 in our fields, instead of in isolated examples as in Nature ; 

 and that the fact of the almost total absence of flowers and 

 fruit in many cultivated varieties shows that the plant 

 is in a disorganised state. Mr. Baker, from an examina- 

 tion of a large number of examples, has come to the con- 

 clusion that all the garden varieties have originated from 

 S. tuberosum, L. Out of 700 or 900 species of Solanum 

 it appears that only six produce tubers or potatoes at all ; 

 the rest " maintain their hold on the world as most plants 

 do, by their flowers, fruits, and seeds." 



Other observers hold an opinion at variance with tlie 



