ProcccdiuiTs of the Ohio State Academy of Science 123 



4. Leaves broadly ovate or suhorhicular : terminal winter btids rounded 



or only slightly angular. 7. 



5. Trees of tall, narrow growth with strongly erect branches, giving a 



spire-like appearance, young twigs glabrous ; leaves usually wider 

 than long, more or less acute at the base. P. dilatata. 



5. Trees with spreading branches. C>. 



0. Young leaves pubescent: capsules nearly sessile. P. nigra. 



6. Young leaves not pubescent, shining; capsules slender-pedicelled. P. 



deltoides. 



7. Leaves coarsely sinuate-dentate, densely white-tomentose when young, 



glabrous when mature. F. grandidentata. 

 7. Leaves crenulate-dentate, glabrous except the ciliate margins. P. 

 trcmidoidcs. 



1. Populus alba L. W'liitc Toplar. .V lar^e tree with 

 smooth, hght, greeni.'^h-gra\- hark often with hlack chamond- 

 shaperl scar.N ; sproitting freeh' from the roots and hence not de- 

 sirahle for yards. Young fohage densely white-tomentose, the 

 leaves becoming glabrate and dark green above, broadly ovate or 

 nearly orbictilar in outline, 3-5 lober], or irregularly dentate, 2-4 

 in. long. Xative of Ettro]:)e and .\sia. ( )hio. 



2. Populus heterophylla L. Swamp Poplar. An ir- 

 regularlv branching tree with rough bark. Leaves long-petioled, 

 boardlv ovate, crenulate-denticulate, 5-^1 in. long. In swamps. 

 Conn, to (Ja., west to La. and nortliward to .\rk., Ind. and Ohio. 



3. Populus balsamifera L. Balsam Poplar. \ large 

 tree with nearly smooth gray b.ark. Leaxcs broadly ovate, 

 dark green and shining above. ])ale beneath, rotmded or acute 

 at the base, crenulate, 3-5 in. long. A\'ood very liglit and 

 soft. In moist or dry soil, commonly along streams and 

 lakes. The subspecies P. balsamifera candicans (Ait.) Gr. 

 Balm-of-Gilead, has the leaves broadly ovate, truncate or 

 cordate at the base, and the petioles and nerves usually 

 puberulent. Mostly escaped from cultivation. Newf. to 

 Alaska, south to N. Y., Ohio, Neb., and Nev. 



4. Populus nigra L. Black Poplar. A large tree with 

 terete twigs. Mature leaves firm, broadly deltoid, abruptly ac- 

 uminate at tlie apex, broadly cimeate or obtuse at the base, cre- 

 nate. 2-4 in. long. Xaturalized from Europe. N. Y. and south- 

 ward alont-- tlie Delaware 1\. 



