NOTES ON POPULUS, PLINIUS 35 
I have observed this species in a number of places, particularly 
at Notre Dame, Indiana, and at St. Joseph, Michigan. 
Populus tremuloides (9 Davisiana (fig. 10). 
Differt a forma typica foliis majoribus suborbicularibus 6-7 
cm. longis, conspicue calloso-serrulatis: gemmis ovatis viscosts. 
Collected at Richmond, Ohio, Aug. 5, 1910 by Prof. C. A. 
Davis, U. S. Bureau of Mines. 
VI. Populus aurea. 
Populus tremuloides Auct..Amer. pro parte. 
Arbor mediocris, cortice cano nonnumquam flavo-viridescents 
-ramulorum suffusco: gemmis glabris, viscosis, conicis, castanets: 
stipulis angustis, 15 mm. longis, caducis: foliis suborbicularibus, 
abrupte acuminatis integris vel serrulatis, trinerviis, glabris, subtus 
glaucis; surculorum (fig. 6) majoribus bast truncatis vel cordatts, 
serrulatis; petiolo limbo breviore vel eum aequanti; amentis masculis 
circa 4 cm. longis, bracteis irregulariter laciniatis, sericeis (f. 3), 
5 mm. plus minus longis: amentis femineis circa 4 cm. longis, 
bracteis laciniatis sericeis, 5 mm. longis: cupula (f. 4.) 2 mm. longa 
diaphana, basin versus valde angustata, stiprtata, margine paulum 
eroso; stigmatibus sessilibus. 
This species differs from P. tremuloides in its shorter and less 
dense aments, in its larger and more irregularly cleft bracts, in 
its larger anthers and the broader and shorter, somewhat trans- 
lucent cupulae of the pistillate flowers. The leaves of P. tremu- 
loides turn light yellow after frost, while those of P. aurea take on 
a golden or an orange hue. P. aurea forms forests throughout 
Colorado, Utah, and adjoining territory,.at an elevation of 2400 
meters and upward. 
Typical flowering material examined: L. F. Ward no. 131, 
Aquarius Plateau, Utah, May 29, 1875; M. E. Jones no. 5169, 
Silver Reef, Utah, May 5, 1894; Tidestrom No. 2153, Horse Fly 
Mountain, Uncompahgre Plateau, Colorado, May 31, 1909; and 
No. 3448, (type), Vicinity of Mount Carbon, May 29, 1910. 
Bureau of Plant Industry, 
Washington, D. C. 
