On the Cultivated Potato. 
291 
upon the bottom lands have been the first to wither away. The 
potatoes in the hills under many healthy vines, when cut open, 
are also found rotten at the centre from wet." * 
Before taking leave of the vast Continent of America to con- 
sider home investigations in our own House of Commons, I beg 
leave to acknowledge, from the author, Mr. Lemmon's very 
interesting account of the " Discovery of the Potato in the 
Arizona," a paper read before the California Academy of Sciences, 
San Francisco, on January 15, 1883. I have, as previously 
mentioned in my own garden, a plant or two of this potato, S. 
Jamcsii of Torrey, and also the S. Maglia.\ The Arizona 
country I take to be about lat. 33° N. I have quoted Mr. 
Lemmon in several places ; I should here mention further that 
I gather from p. 8 that Maglia has a double signification ; it is 
the recognised botanical name of a known species, and also the 
Chilian native name for the wild bitter potato as distinguished 
from the long-cultivated varieties which generally they call 
" Pogny." Mr. Lemmon, under the local designation — as " of 
England " — flatters me by a mention of my name and of my 
known interest in the subject : he mentions also the Royal 
Agricultural Society and our ninety-four essays in 1872, none 
of which solved the difficulty, but most of the writers were 
agreed as to the underlying cause — degeneracy. Mr. Lemmon 
says further — the best American cultivators are of opinion that 
long cultivation of the potato with unchanged conditions results 
in weakness of the constitution, followed by disease, decay, and 
dissolution. 
The scientific and practical aspects of the subject are' abso- 
lutely fixed to that date by the evidence collected, and by the 
Report of the House of Commons Committee of 1880. The 
nature of the potato-disease of 1845, according to the evidence, 
consists in the growth on or in the plant of a fungus, Pero- 
nospora infestans. There is a conflict of testimony as to 
whether the fungoid or mouldy devastation was then intro- 
duced, or whether it previously existed in a modified form, and 
was rendered virulent by exceptional weather. All the witnesses 
concur in a necessity for the production of new varieties ; | all 
* ' Morning Post,' Sept. 25tb, 1883. 
t I have given my little stock of tubers to Messrs. Sutton of Eeading, as their 
collection of cultivated types in a living state is said to be the most complete 
in existence. I am promised that the different species shall be as perfectly hybri- 
dised as possible. 
X Mr. Tliistletoii Dyer, F.R.S., Assist. Director, Royal Gardens, Kew, one of 
ihe witnesses in question, has done me the favour to make the following note on 
my proof. " I doubt this, but I do not doubt the possibility (not necessarily 
practicability) of eventually getting disease-resisting kinds." i\rr. Dyer's idea 
is that in this paper we lay too much stress on the consequences of deterioration. 
u 2 
