which yields it is an entirely new species. Schiede introduced 
the plant tOr the first time into England; and it has been culti¬ 
vated in various Botanic Gardens of Germany. In this country, 
it was probably hret grown in the Botanic Garden of Edinburgh, 
from a tuber, sent by Dr. Coxe of Philadelphia to Dr. Cluristisoii, 
in 183S. The late Dr. Graham could not describe it at that 
time, because, owing to ignorance of its habits, it was forced 
in the stove, and died the same year, after showing number¬ 
less flower-buds, of which one only became partially deve¬ 
loped. In 1844, a plant, from the Chelsea Botanic Garden, 
cultivated in a cold frame during the winter and spring, and 
uncovered during summer and autumn, flowered luxuriantly in 
the Edinburgh Garden, in the month of September. But the 
crown of the tuber w^as injured by frost the subsequent winter, 
and the tuber was thus killed. A drawing w as made by Dr. 
Graham, but it has not been found among his papers. Fortu¬ 
nately, Mr. M’Nab, on removing specimens for the Herbarium, 
resolved to try whether the plant could be raised from slips, and 
the experiment has proved completely successful. A tuber of 
the size of a hasel-nut, formed in the course of three months. 
The stem made little progress the next summer, but w'hen re¬ 
moved to the cold frame last spring, formed the plant from 
W'hich the description and drawing have been taken. 
The plant belongs to the genus Exogonium of Choisy, as defined 
in De Candolle’s ‘ Prodromus,’ although the author places it under 
the genus Ipomoea, from w hich it is at once distinguished by 
its exserted stamens. It grows on the Mountains of Mexico. 
Schiede found it at a great elevation, on the eastern slope of the 
Mexican Andes, near Chiconquinaco; and also on the eastern 
slope of Cofre de Perote. He gives an account of his discovery 
in the ‘Linnaea’ for 1830. Hartweg gathered it in Mexico, 
and it has been described by Bentham, from liis specimens. 
Descr. Tuber roundish, becoming as large as a moderate-sized 
turnip, brown externally, whitish internally, giving rise to nume¬ 
rous rootlets and stems. Stem twining from right to left, spirally 
twisted, glabrous, marked wdth numerous ridges and furrows 
(twenty or more), branching more or less, purple-red, extending 
ten or twelve feet. Leaves alternate, exstipulate, petiolate, cordate 
or sagittato-cordate, deeply lobed at the base, acuminate, entire, 
glabrous on both sides, slightly rugose, dull green above, pale 
or subglaucous below, reticulated; veins radiating at the base, 
prominent on the low^er surface of the leaf and channelled on the 
upper. Petioles about twu inches long, shorter than the leaves, 
thick, grooved above, rounded below^ Peduncles reddish, axil¬ 
lary, erect, twisted, wiry, about one inch and a half long, two- to 
three-flowered (rarely one-flowured) with a small triangular 
