21 
30. Populus tristis, Fisch. P. candicans, of some gardens , 
and perhaps of Wilklenow. 
Tree middle sized, distorted, with a black and almost 
mournful aspect ; branches terete, thick, dark brown ; buds 
swollen, yielding balsam abundantly, resin smelling like 
rhubarb. 
Stipules acute, spreading, balsamiferous. 
Petioles in adult trees long, weaker and laxer than in the 
allied species, with an open furrow passing to their apex, 
where it is depressed and dilated, often equal to half the 
length of the blade of the leaves. 
Leaves in consequence of the weakness of the petioles lax, 
somewhat pendulous, less flat than in the preceding, and often 
more or less concave and waved, ovate, generally cordate, 
acuminate, with the point less elongated and acute than in 
the preceding species, with the base at the insertion of the 
petiole frequently very slightly cuneate ; oblong and sometimes 
oblong-lanceolate leaves are occasionally found mixed with 
the rest. Basal nerves fine ; lateral ones much slenderer ; 
margin of the leaves coarsely crenate ; crenatures sometimes 
double, sometimes incurved, never so indistinct as in the pre- 
ceding species. Leaves smooth, particularly coriaceous and 
strong, above shining, dark green, beneath whitish green, 
opaque, much reticulated, and when old rust-coloured. 
Leaves of young trees, like those on the branches of adult 
ones, but larger, more cordate, with large crenatures. 
N.B. Willdenow’s description of Populus candicans an- 
swers very well to this tree. Its dark, almost black green 
leaves, with their loose drooping position, distinguish the 
plant even at a distance. No species abounds so much in 
balsam. It is to all appearance of American origin. 
31. Populus longifolia, Fisch. 
Trees when young elegantly pyramidal, intensely green ; 
branches upright, spreading erectly, terete, dark brown ; buds 
swollen, with an abundant resin, wdiich smells of rhubarb. 
Stipules spreading, acute, balsamiferous. 
Petioles six times shorter than the blade of the leaf, strong, 
roundish, with an open furrow passing from the base to the 
apex. 
Leaves erect, flat, oblong-lanceolate or lanceolate, gradu- 
ally attenuated towards the apex which is obtuse, with the 
