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SOLANUM COMMERSONII, 385 
SOLANUM COMMERSONII (THE SWAMP POTATO). 
By Professor Wirrmack, of Berlin. 
Soravuw Comuersoni is a potato of the eastern coast of South America, 
not of the western, whence we suppose S. tuberosum to have come. It 
was first found by Commerson in 1767 in the neighbourhood of Monte- 
video, on the banks of the river Mercedes. Later on, S. Ohrondii, which 
was found in the sand of an island in the mouth of the Plata River near - 
Montevideo, was established as a distinct species, but it now appears to 
be identical with S. Commersonii. 
In the year 1896 Prof. Heckel, of the Botanical Garden at Marseilles, 
received some tubers of a potato from Uruguay and determined them as 
S. Commersoniu ; and he was absolutely right. In 1903 he had the kind- 
ness to send me some tubers from it, and I cultivated them in the 
economic garden of our Agricultural High School at Berlin. It is a low- 
growing plant with remarkably long stolons, a metre or more in length. 
The tubers are small, of a pale yellow colour, and have many lenticels. 
Their taste was at first: bitter, as Dr. Heckel reported. The leaves are 
interrupted pinnatifid, the single pairs very distant from each other and 
somewhat blunt, never so sharply pointed as in the common potato. 
The single pairs do not cover the next pair. The flowers are white and 
of a very agreeable odour, somewhat like sweet peas or a little more like 
honey. They are deeply divided, much deeper than with S. twheroswm, 
and forming a star as in the tomato, for which Commerson mistook it. 
In opening in the morning the corolla reflexes, and afterwards, at noon, it 
closes ; the next morning it opens again. 
By the kindness of Messrs. Sutton of Reading, I am able to show 
flowers of S. Commersonii and of its violet variety, as well as of the 
‘Blue Giant,’ a variety of the common potato, and also of S. Maglia, 
S. etuberoswm, and other wild species. 
The chief difference between S. Commersoniw and S. tuberosum lies 
in the calyx. The calyx teeth are short and triangular, whilst in S, 
tuberosum they are long and awl-shaped (subulate). This is a character 
which never changes in our common potato, and one must, as Darwin 
and De Candolle have said, pay special attention to the characters of such 
organs aS man does not use. 
Monsieur Labergerie, a gentleman living at Verriéres, Dép. Vienne, 
France, also had tubers from Dr. Heckel, and cultivated them with great 
care, on highly fertilised soil. 
In the very first year a strange thing happened: A blue or violet- 
coloured potato was found under one plant, and this M. Labergerie pro- 
pagated. He found that it produced large tubers and in great abundance, 
and in 1906 he offered it for the first time in commerce under the name 
of “ S. Commersonii type or variété violette.”’ 
BB 
