CONIFERS. (PINE FAMILY.) 431 



long, sometimes pubescent at maturity, like the branchlets. Fertile aments 

 3'- 4' long. 



The Weeping-Willow (S. Babylonica, Town.), and the Yellow Willow 

 or Golden OfUKB (S. vitcllina, Snath), are introduced species. 



2. POPULXJS, Tourn. Cottox-Wood. Poplar. Aspev. 



Bracts of the aments toothed or lobed. Flowers from an oblique cup-shaped 

 disk. Stamens few or numerous, with the filaments free. Stigmas elongated, 

 2-parted. — Trees. Leaves ovate or roundish, on long and often laterally com- 

 pressed petioles. Buds covered with imbricated, often resinous-coated scales. 

 Aments slender, drooping, appearing before the leaves. 



1. P. angulata, Ait. Branches thick, smooth, and sharply angled ; leaves 

 large, smooth, deltoid-ovate, acute or slightly acuminate, truncate at the base, 

 obtusely serrate with incurved teeth; the conspicuous veins and compressed peti- 

 ole yellowish. — Banks of rivers, Florida, and northward. March and April. 

 — A large tree. Leaves 6' - 8' long, longer than the petiole. 



2. P. grandidentata, Michx. Branches terete; leaves round-ovate, 

 acute, sinuate-toothed, hoary-tomentose when young, like the branchlets, at 

 length smooth, scarcely longer than the slender compressed petiole ; fruiting 

 aments elongated, pubescent. — Low woods in the upper districts, and northward. 

 March and April. — A middle-sized tree, with smooth gray bark. Leaves 3' -5' 

 long, and nearly of the same width. 



3. P. heterophylla, L. Branches terete ; leaves ovate, mostly obtuse, 

 serrate, with oUuse, incurved teeth, rounded or with a small sinus at the base, 

 hoary-tomentose on both sides when young, like the nearly terete petioles and 

 branchlets, at length only on the veins beneath; fruiting aments smooth. — 

 River-swamps in the middle and upper districts, Mississippi to North Carolina, 

 and northward. March and April. — A large tree. Leaves 3' -5' long. 



The Lombardy Poplar (P. dilatata, Ait.), and the White Poplar (P. 

 alba, L.), are introduced species. 



Subclass II. GYMNOSPERMJE. 



Ovules naked (not enclosed in an ovary), commonly sup- 

 ported by an open scale or leaf, and fertilized by the direct 

 application of the pollen. Cotyledons often more than two. 



Order 132. CONIFERS. (Pine Family.) 



Trees or shrubs, with branching stems, composed of glandular or disk- 

 bearing woody tissue without ducts, resinous juice, linear or needle-shaped 



