21 



30. Populus tristis, Fisch. P. candicans, of some gardens, 

 and perhaps of Willdenow. 



Tree middle sized, distorted, with a black and almost 

 mournful aspect ; brancheg 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 equnl 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 m 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. 



NB. 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 5*^?^ 

 branches upright spreading erectly terete, dark bro*n buds 

 swollen, with an abundant resin, which smells of rhubarb. 



Stipules spreading, acute balsamiferous 



Petioles six times shorter than the blade of the leaf strong 

 roundish, withan open furrow passing from the base to 



^Leaves erect, flat, oblong-lanceolate or *£*^ 

 allv attenuated towards the apex which is obtuse, with 



