On the Cultivated Potato. 
279 
potato-plant designed as a suitable and natural matrix for all 
these plagues ? " 
Scab is a disease of the tuber, a fungus, Tiihercinia scabies ; * 
dry rot is also a fungus of the same order, Fusisporium solani. 
This last was first observed in Germany in 1830, where through 
many years it is supposed to have caused great loss. Wet rot 
is also fungoid, said to be a fungus of the same type as the dry 
rot. And this Fusiporium'\ is a little friend and constant com- 
panion of the fungus, inseparably associated with the disease 
of 1845, namely, the Peronospora infestans. 
We are now brought to the disastrous year of 1845, the year 
of the great outbreak of potato-disease, a new form of an old 
disease,f which inaccurately has been called by many confusing 
names, as plague, and murrain. This disease is specially charac- 
terized by the full recognition of its fungoid attendant, Perono- 
spora infestans, the disease shall in future be simply designated 
by me as the potato disease of 1845. It appeared in St. Helena 
in 1840 ; detected in England here and there the following year ; 
it appeared at various periods about this time in North America ; 
both continents were affected. The disease burst out generally 
in 1845, and swept whole districts throughout Europe, leaving 
in its track of devastation famine and suffering and human 
misery. 
From this general historical retrospect we now turn to glance 
at the particular history of several branches of the inquiry. The 
sum of all history goes, in my opinion, to show that the culti- 
vated potato-plant has an inherent tendency to degenerate — 
a factor which consequently must always enter into the problem 
of the causes of special manifestations of disease ; and history 
further tells us that throughout there has been almost a uni- 
versal clamour for new varieties. § 
The physiology of the potato has yet to be written ; || that is 
* Dr. Cooke, of Kew, author of the ' Handbook of British Fungi,' has favoured 
mc with the following note ; — Now called SoroBporutm t-cahies, and classed with 
the Ustilagines, or " Smut " and " Bunt " of corn. See Fischer de Waldheim, 
' Annales des Sciences Naturelles (Botanique),' ser. 6, vol. iv. (1876), p. 229. 
t Keport, House of Commons Committee, 1880. 
X Report, Scotch Committee of Scientific Men. Tiie Groningen Commission 
said the disease had been long known. 
§ See, in regard to the time present, an excellent letter from a practical cultivator 
and hybridiser, Mr. Robert Fenn; he hails with great satisfaction the idea of the 
<S. Maglia having, as regards varieties, come to the end of his tether. Mr. Fenn 
happily describes the potato as the " Cinderella of Nature." — ' Journal of Horti- 
culture,' Feb. 7, 1884. 
II " The physiology of the potato has yet to be written." I should demur to ex- 
pressing it in this form, because there is no ground for supposing that the potato 
furnishes any exception to the general laws that regulate the life of all plants. 
The roots and leaves between them absorb the food, and it is cooked up in the 
leaves, and they furnish the nourishment needed to build up the flowers and 
