294 SYSTEMATIC BOTANY. 



6. Carpinus. Barren flowers in drooping, cylindrical aments ; 

 stamens 8-12, furnished with a roundish, ciliate bract instead of a 

 calyx ; filaments very short ; anthers bearded at apex. Fertile flowers 

 mostly in twos, each pair with a small, deciduous bract, contained in a 

 large, 3-lobed involucre, each flower with a 2-celled, 2-ovuled ovary, 

 terminating in 2 filiform stigmas. Nuts small, ovoid, furnished with 

 an enlarged, open, and leaf-like scale. Trees. 



C. AMERICANA (Hornbeam). Leaves oval or oblong-ovate, acuminate, 

 acutely and unequally serrate, petiolate ; fruiting aments drooping, long, 

 loose, with the dark-brown nuts arranged by twos, each with an involucre. 

 A small tree. April-May. 



7. Betula. Barren flowers in cylindric aments, each bract with 

 3 flowers, each flower consisting of 4 stamens. Fertile flowers in ob- 

 long-ovoid aments, 3 to each bract, with no calyx, each consisting of 

 an ovary with 2 filiform stigmas. Fruit compressed. Trees. 



1. B. LENTA (Black Birch). Leaves ovate, serrate, cordate at base, 

 acuminate, hairy on the veins beneath, as also the petioles ; fertile aments 

 oval, erect, somewhat hairy ; lobes of the scales obtuse. A tree of rather 

 large size, common in forests. April-May. 



2. B. PAPYRACEA (Paper Birch). Leaves ovate, acuminate, mostly cor- 

 date or obtuse at base, doubly serrate, dark green and smooth above, hairy 

 on the veins beneath. A large tree. April-May. 



3. B. ALBA, var. POPULIFOLIA (White Birch). Leaves deltoid, with a 

 very long acuminate point, truncate or hearted at base, smooth, and of a 

 bright, shining green on both sides. A very slender and graceful tree, com- 

 mon in rocky woods and thickets. April-May. 



8. Alnus. Barren flowers in long, cylindrical, nodding aments ; 

 scales 3-lobed, 3-flowered ; flowers with a 4-parted calyx and 4 stamens. 

 Fertile flowers in ovoid aments ; bracts fleshy, 2-flowered, 3-lobed ; 

 calyx-scales 4, minute. Shrubs. 



1. A. INCANA (Hoary Alder). Leaves broad-oval or ovate, somewhat 

 cordate at base, sharply serrate, sometimes coarsely toothed, mostly white- 

 downy underneath ; stipules oblong-lanceolate ; fertile aments oval. A 

 shrub, 8-15 feet high. March-April. 



2. A. SERRULATA (Common Alder). Leaves obovate, acuminate, taper- 

 ing at base, sharply and finely serrate, smooth and green on both sides, 

 somewhat pubescent on the veins beneath ; fertile aments oblong-oval ; fruit 

 ovate. A common shrub, 6-15 feet high. March-April. 



Order LXXVIIL SALICACE^E ( Willow Family}. 



Trees, or shrubs, rarely somewhat herbaceous. Leaves alter- 

 nate, simple, with deciduous or persistent stipules. Flowers dice- 



