January 24, 1884. ] 
JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 
57 
24 
Th 
Royal Society at 4.30 p.M. 
25 
P 
Quekett Club at 8 P.m. 
26 
S 
Royal Botanic Society at 3.45 P.M. 
27 
SUN 
3rd Sunday after Epiphany. 
28 
2D 
M 
Royal Geographical Society at 8.30 P.M. 
30 
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Society of Arts at 8 P.M. 
HYBRIDISING- POTATOES. 
NEW phase of that highly important subject, 
the production of disease-resisting Potatoes, has 
been opened by Mr. Baker of Kew, who, at the 
last meeting of the Linnean Society, gave the 
outline of a series of exhaustive researches and 
observations respecting the tuber-bearing species 
of Solanum. His investigations were under¬ 
taken at the request of Lord Cathcart, and the 
object was to determine the number of really 
distinct tuberous Solanums, their distribution, and the 
characters of the climates to which they are peculiar. To 
effect this satisfactorily it was found necessary not only to 
carefully compare a very large number of specimens from the 
various districts of North and South America with the 
descriptions given by botanists who have reviewed the genus, 
but also to determine the range of variation in the Potatoes 
cultivated in English gardens. The latter portion of the 
task was undertaken last autumn, and the varieties grown in 
the grounds of the principal seedsmen were fully examined 
and classified, one result being that Mr. Baker considers it 
incontestably proved that all are descended from the true 
Solanum tuberosum, and that no other species has played 
any part in the production of cultivated Potatoes. 
This point being settled, it became necessary to determine 
how many of the tuberous Solanums described in botanical 
works merit the rank of species, and the conclusions arrived 
at under this head were that the majority of those mentioned 
in Decandolle’s “ Prodromus ” and other works are simply 
varieties of S. tuberosum, and that, including this, only six 
well-marked species can be named— i.e., S. Maglia, S. Com- 
mersoni, S. cardiophyllum, S oxycarpum, and S. Jamesi. 
These extend in geographical range from Chili to New 
Mexico and the Rocky Mountains, and consequently inhabit 
climates varying greatly in temperature and humidity, both 
of which have an important bearing upon the adaptation of 
the progeny of such species to cultivation in the British 
Islands. In Chili is found the true S. tuberosum, which 
grows wild at great elevations in the Andes, where at least 
for a great portion of the year the climate is exceedingly dry, 
and therefore differing considerably from the average English 
climate. 
In the lower portions of the district, in the valleys, and as 
the coast is approached, the humidity is greatly increased 
until the rainfall is very high and the vegetation correspond¬ 
ingly luxuriant. There is found the 8. Maglia of Baker, 
which he considers easily separable from S. tuberosum by 
characters of the foliage, flowers, and fruit, which need not be 
detailed here. It produces tubers of moderate size, 2 to 
8 inches long, somewhat kidney-shaped, solid, and when 
cooked of fair flavour, evidently possessing a large quantity 
of starch. This has been grown at Kew for nearly twenty 
years, but has been generally regarded as the true S. tuber¬ 
osum. It is perfectly hardy, the roots being left out unpro¬ 
tected, is very strong in habit, with broad leafl-ts, and it has 
not been attacked by disease, the produce being abundant 
No. 187.— Vol. VIII., Third Series. 
and regular. Sixty years ago a coloured plate and descrip¬ 
tion of the so-called wild S. tuberosum was given in vol. v. 
of the London Horticultural Society’s Transactions, 
together with a full description and results of its culture in 
the Society’s gardens, by the then Secretary, Mr. Joseph 
Sabine. This Mr. Baker considers to be really S. Maglia, 
and as the results there given are very favourable, he regards 
it as good evidence of what careful cultivation might effect. 
In “A Naturalist’s Voyage Round the World” Darwin 
referred to the wild S. tuberosum as being found in damp 
forests of the lower parts of Chili and in the neighbourhood 
of Valparaiso, and comments upon the remarkable range of 
climate the plant endures, from the arid regions of the Andes 
to the humid districts in the lower parts. Here again Mr. 
Baker regards S. Maglia as the subject of Darwin's observa¬ 
tions, and not S. tuberosum as was supposed; and many 
other facts were adduced to prove that the two species had 
been confounded by travellers and botanists. 
A third species, S. Commersoni, is found in Brazil, and 
is very distinct from the two former, being of slender habit, 
with small leaflets and deeply cleft corollas. This has been 
recently introduced to the Continent under the name of 
S. Ohrondi, but has never been cultivated in England. It 
has small tubers, said to be of good quality when cooked, 
but less is known respecting it than of S. Maglia, though pro¬ 
bably more will be heard of its characters during the coming 
season. Many forms are found in Brazil, but they are all 
referred to this species. 
Mexico claims three species—viz., S. cardiophyllum, 
S. oxycarpum, and S. Jamesi; but the only one of these that 
appears likely to prove of horticultural importance is the 
last-named, which has been grown at Kew during the past 
year. It is of dwarf habit, with small leaflets and deeply 
cleft corollas, like S. Commersoni, and bears very small 
tubers, none at present grown exceeding 1 inch in diameter; 
but they are very numerous, and when cooked extremely 
floury and pleasantly flavoured. 
The practical result of these investigations is that Mr. 
Baker recommends the culture of S. Maglia and S. Com¬ 
mersoni for hybridisation with S. tuberosum, with the 
object of raising a type of Potato that should, if possible, 
unite the prolificness, good quality, and size of tuber of the 
latter with the damp-enduring character of the former, 
which would be likely to render Potatoes more adapted for 
our moist climate, and, therefore, less liable to disease. The 
importance of this suggestion, and the reliability of the 
facts upon which it is advanced, render it well worthy the 
attention of all who desire to improve this vegetable, and 
the thorough manner in which the investigations have been 
conducted merit the highest commendation. 
If, as appears more than probable, that the species, 
S. Maglia especially, possesses greater inherent vigour, and 
is naturally adapted for a moist climate, it necessarily has 
claims to the attention of hybridisers of distinctly greater 
importance than those of S. tuberosum, which for the past 
century cultivators have been so busily engaged in improving. 
As far as regards the productiveness and quality of our best 
varieties there is little to be desired, but a greater disease- 
resisting power is urgently needed. It is the more likely 
that this may be imparted by the robust and moisture- 
enduring species S. Maglia, since experience has shown that 
vigour of plant is an element of success, inasmuch as with 
scarcely an exception what are termed “ disease-resisting ” 
late or main crop varieties are strong growers with more or 
less ligneous stems and robust foliage. It is also established 
as a rule with only the few exceptions necessary to prove its 
existence, that an excess of moisture in the soil and the air 
at a critical period of the plant’s growth is the great pre¬ 
disposing cause of the murrain that devastates the crops. It 
is seldom virulent in dry years, but always more or less so 
in wet ones. Varieties that ripen very early, and especially 
when grown in dry warm positions, are rarely seriously 
No. 1843. —Yol. LXX., Old Series. 
