196 Rhodora [SEPTEMBER 
Any one who has travelled in Delaware or portions of Maryland, 
where poplars are usually found planted about farm houses, might 
readily have observed these majestic trees with large and spreading 
branches and broad crowns. Perhaps Marshall described a cultivated 
tree of his own region, but not knowing its origin, and thinking it 
the same as Bartram’s P. deltoides, ascribed it to Carolina and Florida. 
Schneider! cites Populus marilandica Poiret? as a synonym of 
P. deltoides. The description, however, is not sufficient to identify 
the species of Poiret, since nothing is said about the leaves on the new 
growth, which differ both in form and size from those of the branches. 
In our concept of species, particularly where we deal with the Sali- 
caceae, and for that matter with some groups outside of this family, 
it is absolutely necessary to take account of the new growth. 
In Europe where many of our American poplars have been culti- 
vated for more than a century, traditions have aided in the clearing up 
of the species and their synonymy. Ascherson and Graebner * have 
two forms, “subspecies,” under their aggregate (Gesammtart) Populus 
canadensis. The first appears under this name while the second is 
held to be Populus virginiana Fougeroux. They describe the leaves 
of P. canadensis as follows: “Blätter aus kaum herzfórmigem, gera- 
dem, oder meist kurz keilfórmigem Grunde, breit-eifórmig bis fast 
rhombisch, zugespitzt, am Rande ziemlich regelmässig gesägt, die 
unteren der Aeste am Grunde vorgezogen, der Vorsprung am Blattstiel 
meist einen rechten Winkel bildend, an der Einfügung des Stieles 
meist mit 2 Drüsen, alle am Rande oder anliegend behaart, an kráf- 
tigen Treiben bis über 1 dm. lang und breit." I take this descrip- 
tion to apply to the tree which we know as P. deltoides. As Ascherson 
and Graebner state, the leaves are very variable, but usually somewhat 
rounded at the base, serrate with incurved teeth and acuminate. 
The larger leaves of the root-shoots, uppermost branchlets, etc., 
are truncate at the base and acute,— thus somewhat “deltoid.” 
'The petioles of both forms are usually equal in length to or longer 
than the leaf-blade. A good illustration of the ordinary leaf-form is 
given in Bailey’s Cyclopedia 5: 1410, f. 1913, while the larger form 
is given under f. 1912. Populus deltoides is à pyramidal tree when 
young but when older, and particularly when free to expand, it be- 
1 Illustr. Handb. Laubh. 1: 7, 1906. 
2? Lam. Enc. Suppl. 4: 378, 1816. 
3 Syn. Mitteleurop. Flora 4: 33, 1908. 
