This notice is intended as a supplement to the observations read last session by the author, on the composition and sources of the different kinds of Gamboge. It is well known that Linnæus referred gamboge to the Garcinia cambogia, Willd.; and others have supposed that a kind of gamboge is also produced by the Xanthochymus pictorius. Both are natives of Ceylon, where, as appears from the former investigations of the author, a substance is produced almost or absolutely identical with Siam gamboge. It appeared, however, from the inquiries of Dr Graham, read before the Society last session, that this Ceylon gamboge is produced by an undescribed species of tree, and not by either of the species just mentioned.