18 ELEMENTS OF BOTANY. 
roundish ovate and irregularly sinuate-toothed, when young com- 
pletely covered with white silky wool, which is shed as soon as the 
leaf matures. ‘The petiole is somew hat flattened, but not nearly as 
ee so as that of the preceding species. 
(P. MONILIFERA), Corronwoop. A large and very rapidly 
epg tree, 75 to 100 or more ft. in height, often with a markedly 
excurrent trunk (Fig. 26). Leaves large and broadly triangular, 
with crenate-serrate margins and long tapering acute tips; petioles 
long and considerably flattened. The numerous pediceled capsules 
are quite conspicuous when mature, and the air is filled with the 
downy seeds at the time when the capsules open. 
CUPULIFERZ, OAK FAMILY. 
Moncecious trees or shrubs. Leaves alternate, simple, 
straight-veined, with deciduous stipules. The staminate 
flowers are generally in catkins, the pistillate ones some- 
times in catkins, sometimes not. The ovary is several-celled, 
with one or two ovules in each cell, but only one ovule 
matures to form the fruit, which is a 1-celled and 1-seeded 
nut (Fig. 170). 
I. BETULA, BIRCH. 
Flowers opening in early spring, the staminate ones in 
long and drooping bright yellow catkins, which appear with 
or before the leaves, the pistillate ones in much shorter and 
stouter catkins. Each scale of the staminate catkins bears 3 
flowers, which consist mainly of two 2-parted filaments, with 
an anther-cell on each. On every scale of the pistillate cat- 
kins are borne 2 or 5 flowers, each of which consists simply 
of a naked ovary with two diverging stigmas. 
a. (B. LENTA), SWEET, BLack, or Cuerry Bircn. Leaves 
and bark with the agreeable smell and flavor of wintergreen. 
Leaves more or less heart-shaped at the base, ovate or nearly so, 
doubly serrate. A tree 50 to 75 ft. high, with beautiful pale rose- 
colored wood, used in cabinet work under the name of red birch. 
b. (B. popULIFOLIA), GRAY Biren. Leaves triangular, with a 
long taper point and truncate base, unevenly twice serrate, with 
longish slender petioles, which allow the leaves to quiver like those 
of the aspen. Bark scaling off in white strips and layers, but not in 
nearly as large sheets as that of the rarer canoe birch (B. papyrifera). 
