The Flora of the Cayuga Lake Basin 163 



4. P. candicans Ait. (/'. balsamifera, var. candicans, of Cayuga Fl.) Balm 



OF GlLEAD. 



Roadsides and low grounds ; infrequent. Apr. 25-May 5. 



Occasionally spreading from cultivation : Mitchell St., Ithaca ; near the East Ithaca 

 railroad station ; upper Cascadilla Creek ; swampy woods n. e. of Mud Pond, McLean 

 Bogs, spreading from a grove of large trees said to have been planted by the early 

 settlers (D.\) ; along Fall Creek, n. of Freeville. 



A much-cultivated tree of doubtful origin, probably a hybrid from Europe. Only 

 the pistillate form is known. It is often confused with P. tacamahacca, var. Michauxii, 

 and perhaps also with pubescent forms of P. tacamahacca itself. 



5. P. tremuloides Michx. American Aspen. Trembling Poplar. 

 Gravelly, sandy, or stony, acid or neutral, soils ; common. Mar. 25-Apr. 15. 

 Scarce about Ithaca ; more common in the hills s. w., s., and s. e. of the city, along 



the cliffs of Cayuga Lake, and in the gravels of the McLean region. 



Newf. and Lab. to Alaska, southw. to Tenn., Mo., and Nebr., including the Atlantic 

 Coastal Plain, and through the western mts. to Mex. and Calif. 



One of the most widely distributed of local trees, common in the North and extend- 

 ing almost or quite to the northern limit of tree growth. 



6. P. grandidentata Michx. Large-toothed Aspen. 



Dry light well-drained soil, chiefly on ravine crests and slopes, occurring in some- 

 what richer soils than the preceding ; common. Apr. 10-30. 



N. B. to Minn., southw. to 111. and Iowa, including the northern Coastal Plain, and 

 in the mts. to N. C. A tree strictly of the northeastern U. S. and of the Great Lakes 

 district in Canada. 



7. P. alba L. White Poplar. Abele. 



Chiefly light soils; occasional. Apr. 25-May 10. 



In cultivation from Eurasia, and sometimes suckering freely in yards and along 

 roadsides, thus becoming a troublesome weed. 



2. Salix (Tourn.) L. 



Key based on staminate floivcrs 1:J 



a. Nectaries 2 (often 3^1 in the first two species) ; scales pale or yellow, not dark- 

 tipped ; filaments hairy ; catkins terminal on strongly leafy-bracted lateral 

 branchlets. 

 b. Stamens more than 2 (nos. 7 and 8 sometimes fall in this group). 



c. Catkins slender (8-12 mm. in diam.), rather loosely flowered; twigs slender, 

 more or less fragile near the base; trees. 

 d. Nectary yellow, pale when dry. 1. S. nigra 



d. Nectary red, blackish when dry. 2. S. amygdaloidcs 



c. Catkins stout, thick (13-20 mm. in diam.), densely flowered; twigs stouter, 

 tough at base ; shrubs. 

 d. Catkins 2-5 cm. long, flowering May 15-30. 3. S. lucida 



d. Catkins 1-1.5 (2) cm. long, flowering June 10-30. 4. S. serissima 



b. Stamens 2 (in nos. 7 and 8, sometimes 3 or 4). 



c. Filaments hairy through more than half their length ; young leaves linear, 

 sessile or nearly so; catkin-bearing branchlets 2.5-8 cm. long below the 

 catkin at flowering time ; low shrubs. 5. 5". longifolia 



c. Filaments hairy only at base ; young leaves lanceolate or elliptical, petioled ; 

 catkin-bearing branchlets less than 2.5 cm. long at flowering time; trees. 



13 Varieties based chiefly on foliage are omitted. Only staminate catkins are referred to in 

 this key. 



