314 
European species in each case, and are 
undoubtedly first-crosses. These two 
trees have been traced back to 1700, 
about which date the American parents 
had been long enough in Europe to 
bear flowers.” 
THE POPLAR HYBRIDS 
The black poplars, it will be remem- 
bered, are represented by only two 
species, one native to Europe and the 
other to North America, and both 
having well-marked geographical varie- 
ties. The European species, Populus 
nigra, is distinguished from the Amer- 
ican tree, Populus deltotdea, by the 
absence of cilia (tiny projecting hairs) 
on the margins of the leaves, and by the 
absence of glands on the base of the 
leaf-blades in front. These character- 
istics are present on the leaves of the 
American black poplar. The author 
designates the glabrous form of the 
European black poplar as Populus nigra 
var. typica, and the pubescent form as 
Populus nigra var. betulifolia. The 
glabrous black poplars of North America 
are given as Populus deltoidea var. 
monolifera, growing from Ontario to 
Pennsylvania, and Populus deltoidea 
var. occidentalis, growing in the region 
directly east of the Rocky Mountains, 
from Saskatchewan and Alberta to 
New Mexico and western Texas. The 
pubescent American black poplar is 
Populus deltoidea var. muissourtensis, 
which grows in the south and south- 
eastern parts of the United States, 
ascending the Mississippi basin to 
Missouri. This variety, the author 
believes, may be taken as the type of 
Populus deltoidea, being most likely to 
be the form represented by the original 
description of Marshall. 
THE CAROLINA POPLAR 
But the chief importance of Prof. 
Henry’s contribution lies in his extensive 
study of the cultivated black poplars, 
which has resulted in the valuable dis- 
covery that they are almost invariably 
of hybrid origin. Most interesting to 
American foresters is the discovery 
made concerning the Carolina poplar 
which has been so extensively cultivated 
here. A great many of our writers 
The Journal of Heredity 
have felt that this name, ‘Carolina 
poplar,’’ was one invented by nursery- 
men to overcome the unpopularity of 
the cottonwood. Some have even 
believed that the Populus nigra of the 
trade was nothing but our Populus 
deltoidea grown in France and Belgium 
and returned to America under the false 
designation. Muchrelief, therefore, will 
be experienced by reputable dealers, and 
by their patrons as well, at having 
Prof. Henry’s determination of the true 
nature of the cultivated black poplars, 
and especially the Carolina poplar. 
Originally the author felt that this 
tree was merely a form of our Populus 
deltoidea, which had undergone mutation 
in its floral parts after cultivation in 
Europe. But now it is determined that 
the tree is a hybrid between the true 
black poplar of Europe (Populus nigra) 
and the southern form of our native 
black poplar (Populus deltotdea var. 
Missouriensts). 
In addition to the Carolina poplar, a 
number of hybrids are illustrated and 
described by Prof. Henry which have 
been derived from the typical black 
poplar of Europe and the northern form 
of our black poplar (Populus deltoidea 
var. monolifera). These are: P. serotina 
Hartig, P. regenerata Schneider, P. 
Eugenet Simon-Louis, P. marilandica 
Bosc., and P. Henryana Dode. Further, 
two forms are described as having arisen 
from the hybridization of the European 
black poplar with hybrid forms. These 
are P. robusta Schneider and P. Lloydiit 
Henry. 
WHY NOT A HYBRID SYCAMORE? 
Viewing this work in the light of the 
previous researches of Prof. Henry on 
the artificial production of vigorous 
trees, it will be observed that the 
author has first demonstrated the prac- 
tical importance of propagating first 
generation hybrids. He has then ascer- 
tained that the poplars already recog- 
nized as especially desirable for cultiva- 
tion are of hybrid origin. The two 
papers, therefore, present most forcibly 
the great importance of initiating inten- 
sive work on the artificial production of 
vigorous trees, and suggest that special 
attention be directed toward the hybrid- 
