162 Karl M. Wiegand and Arthur J. Eames 



c. Leaves coarsely undulate-dentate, tomentose when young ; buds, one-year-old 

 twigs, and capsules puberulent or downy, dull. 6. P. grandidentata 



b. Petioles terete or nearly so : mature leaves white-tomentose beneath ; buds and 

 one-year-old twigs white-tomentose. 7. P. alba 



1. P. balsamifera L. (See Tourn. Arnold Arb. 1:62. 1919. P. deltoides of Gray's 



Man., ed. 7. P. monilifcra of Cayuga Fl.) Cottonwood. Necklace Poplar. 



Low alluvial fields, woods, and shores ; common. Apr. 25-May 10. 



Most abundant on the shores of Cayuga Lake, and in the valleys and ravines of the 

 larger streams in the basin; occasional on the hillsides above the ravines, as in Six 

 Mile and Cascadilla valleys. 



\Y. Que. and X. H. to the Rocky Mts., southw. to Fla. and Tex. ; rare or absent 

 on the Coastal Plain. 



Typical P. balsamifera has very large ovate leaves (12-15 cm. long, 10-12 cm. 

 wide). The common form throughout the range has smaller, ovate-deltoid leaves and 

 is separated from the typical form by Bailey and by Sargent as var. zirginiana 

 (Last.) Sarg. This distinction seems doubtfully worthy of recognition. 



The so-called " Carolina poplar," a tree commonly cultivated because of its rapid, 

 luxuriant growth, is probably of hybrid origin, with P. nigra and P. balsamifera or 

 P. regenerata as parents. It has been called P. Eugenei Simon-Louis and P. cana- 

 densis Moench. but the tree needs further study (see Bailey, Man. Cult. PI., p. 

 226. 1924). This plant spreads from the roots along roadsides and in waste places. 

 It differs from P. balsamifera in the following characters: leaf margin naked 

 or sparsely pubescent, instead of finely ciliate toward base; serrations less 

 coarse and less strongly uncinate ; leaf base generally slightly convex instead of 

 concave ; leaf outline more rounded than deltoid, with a less acuminate apex ; tree 

 narrow- topped, and subcylindrical instead of widespread. 



2. P. nigra L.. var. italica DuRoi. (P. dilatata of Cayuga Fl.) Lombard y Poplar. 

 Roadsides and low grounds ; occasional. Apr. 15-30. 



Commonly cultivated, and occasionally spreading from the roots or by water-borne 

 twigs: C. L". campus; near Spring St.. Ithaca (D.) : on the points along Cayuga Lake, 

 as Myers Point (P.!), Lake Ridge Point (£>.!), Willets (D.) ; and elsewhere. 



This plant is said to be a staminate sport of P. nigra which arose in Lombard}' early 

 in the eighteenth century. It has since been spread over the world by cuttings. 



3. P. tacamahacca Mill. (See Journ. Arnold Arb. 1:61. 1919. P. balsamifera of 



authors and of Cayuga Fl.) Balsam Poplar. Tacamahac. 



Alluvial bottom lands and borders of swamps, or, along the southern limit of the 

 -pedes, in drier rocky soil: rare. Apr. 25-May 15. 



Taughannock Gorge, in woods just n. e. of the falls (D. !). a group of small, 

 slow-growing trees, apparently now much the same as thirty-nine years ago. These 

 trees are " probably indigenous, resembling in habitat and appearance those seen at 

 Niagara and elsewhere" i D. !). Other stations are: near Jacksonville, cultivated, 

 probably from the Taughannock station: s. of Willets, probably introduced ( ZV) : 

 roadside and meadow near White Church (D.. also A. J. E. & L. H. Mac Daniels). 



Xewf. and Lab. to Alaska, southw. across the continent, entering the U. S. only 

 along its northern border ; a tree distinctly of the Far North, reaching its extreme 

 southern limit here. Along the southern boundary of its range it is a poorly developed 

 tree. 



The leaves are generally glabrous but occasionally puberulent on the petioles and 

 veins beneath, such specimens being transitional to the var. Miehauxii (Henry) 

 Farwell. a northern variety not known in the Cayuga Lake Basin. 



