On the Cultivated Potato. 
297 
tuberosum, but S. Maglia, which differs as much from S. tubero- 
sum as any of the species. Solamim tuberosum, from which 
the cultivated potato is considered to originate, is said to be a 
plant of the High Andes of Chili, and surely a plant of the sterile 
mountains of Central Chili, where a drop of rain does not fall for 
six months, and where, as compared with the northern hemi- 
sphere, summer and winter are reversed, is grown in England, 
Scotland, and Ireland under such abnormal conditions, that it is 
not surprising it degenerates and becomes diseased. Far more 
confidence might be placed in S. Maglia, of which the geo- 
graphical requirements resemble our own. When they come 
into flower I would like to compare the leading kinds of the 
potato grown in England with each other and with the wild 
types ; with that view, I will write at once to Mr. Sutton, I 
should go through his fields to see as many varieties as possible, 
and carry away ten or a dozen good specimens of the leading 
types for study. De CandoUe, otherwise admirable, confounds 
S. tuberosum and S. Maglia, as does Sabine, who is otherwise at 
the foundation of our potato knowledge. I send you some S. 
Afaglia tubers to plant, l our notes have been read ; I think we 
may classify matter bearing on the subject under four heads : 
(1) History of the cultivated plant; (2) Its diseases, parasitic 
lungi, and parasitic insects ; (3) Its botanical geography ; (4) Its 
physiology. Subjects 1 and 2 are almost exhausted ; 3 and 4 
comparatively neglected ; 3 is the branch on which I am specially 
'at home. I think we may formulate a general principle such 
as this : every species has a certain range of power and adapta- 
bility as regards soil and climate. If the conditions which it needs 
are not supplied, it will degenerate, become diseased, and finally 
<lie out. You can only acclimatise in a new country by giving 
what is required in the matter of soil and climate : there is 
here a wide field for research and experiment. Touching sub- 
ject 4, see the best Paper that has been written on the physiology 
of the plant, that of T. A. Knight, ' Philosophical Transac- 
tions ' for 1806. No doubt one powerful cause of deterioration 
in the potato is that the tuber has been abnormally stimu- 
lated * at the expense of the rest of the organism. A familiar 
English name for S. Maglia would be " Darwin's Potato." 
Messrs. Sutton were most kind and hospitable ; we have 
spent some time in their trial-grounds (August 11), and have 
obtained many specimens and made many notes. All the in- 
formation to be obtained about the species and their climatic 
* Mr. Thistleton Dyer, F.E.S., notes : " I doubt this ; the Irish Govcrament got 
over a frc&h strain from South America and it suftered just as much as the 
abnormally stimulated varieties." 
