THE CONVOLVULUS 
177 
they are chiefly scentless ; but the jessamine and rose, 
which flourish so well under an Italian sky, and which we 
prize so highly, are, notwithstanding their beauty, rather 
offensive than pleasing. 
The great number of garden species of convolvulus ren- 
ders it useless to particularise them all. The scammony 
of the druggists, a gum-resin much employed in medicine, 
is obtained from the roots of a species of this plant grow- 
ing wild in countries bordering the Mediterranean. The 
Convolvulus scammonia has flowers of a yellow colour. 
The Convolvulus batata, or sweet potato plant, is interest- 
ing, as its root is the potato of Shakespeare and the earlier 
writers. The common potato (Solanum tuberosum) is 
thought to have been introduced into England by the 
unfortunate Sir Walter Raleigh. Owing to a prejudice 
which existed against it, it was not, for many years after- 
wards, used as an article of general consumption. This 
arose from the circumstance that the potato belongs to a 
highly poisonous class of plants, of which the common 
nightshade is an example. The potato, indeed, contains 
poison, which is subdued by boiling; but Linnaeus always 
denounced it as unwholesome. 
The batata, or sweet potato, was highly extolled for its 
restorative virtues; and it was thought to have so much 
power in repairing decayed constitutions, as to have been 
almost a specific for the infirmities of old age. 
The potato convolvulus is a trailing plant, bearing pur- 
ple blossoms and angular leaves. It is now often reared 
in gardens, as an ornament. At every joint of its long 
stem it sends forth a tuber. These tubers are very nume- 
rous upon the plant; and as, in their native soil, they are 
so easily propagated, they form an important article of 
food to the natives of warm countries. They are much 
used for the table in Spain and Portugal, and are annually 
exported from those countries into England. 
The batata was introduced into this country by Sir 
Francis Drake and Sir John Hawkins; and great numbers 
of the roots were brought hither for many years succeeding 
its introduction. The potato of present use being, how- 
ever, better adapted to general culture in this climate, it 
has superseded the use of the sweet potato ; and that plant 
is but little valued amongst us, except as a curiosity, 
