This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Populus Nigra C. B. & Linn. Populus nigra five aigeiros J. B. Black poplar: a large tree; with dark green, somewhat rhom-boidal acuminated leaves; producing imperfect flowers, in catkins: in some of the individuals, called male, the flowers are barren; in others, called female, they are followed by membranous pods, containing a number of seeds winged with down. It is indigenous in watery places, and quick of growth.
The young buds or rudiments of the leaves, which appear in the beginning of the spring, were formerly employed in an officinal ointment, which received its name from them. At present, they are almost entirely disregarded; though they should seem, from their sensible qualities, to be applicable to purposes of some importance. They abound with a yellow, unctuous, odorous, balsamic juice, which they readily impart, by maceration or digestion, to rectified spirit. The tincture, infpiffated, yields a fragrant resin, superiour to many of those brought from abroad, and approach to the nature of storax.
* A species of poplar growing in Siberia and in North America, called by Linnaesus Populus balsamifera, is said to be much more abundant in balsamic juice than the former, insomuch that the buds give it out on mere expression (a).