DICOTYLEDONOUS PLANTS 47 
SUBCLASS II.—DICOTYLEDONOUS PLANTS. 
Stems composed of bark, wood, and pith; the fibro-vascular 
bundles in rings ; in woody stems which live over from year 
to year, the wood generally in annual rings, traversed at right 
angles by medullary rays. Leaves netted-veined. Parts of 
the flower usually in fours or fives. Cotyledons 2 (rarely 
none). ‘ 
14. SALICACEZ. Wuttow Famity. 
Dicecious trees or shrubs, with flowers in catkins (Ch. XIII), 
destitute of floral envelopes. Fruit a 1-celled pod, with 
numerous seeds, provided with rather long and silky down, 
by means of which they are transported by the wind. 
I. POPULUS, Tour. 
Trees with prominent scaly buds, twigs more or less angled. 
Leaves usually long-petioled. 
Flowers borne in long, drooping catkins, which appear 
before the leaves ; scales of the catkins irregularly cut toward 
the tip. Stamens 8-30 or more. Stigmas 2-4. Capsules 
opening early by 2 to 4 valves. 
1. P. tremuloides, Michx. AMERICAN ASPEN, QuUAKING Asp. A 
tree 20 to 60 ft. high, with greenish-white bark; leaves roundish, 
heart-shaped, abruptly pointed, with small regular teeth. Leaf- 
stalk long, slender, and flattened at right angles to the broad 
surfaces of the leaf, causing it to sway edgewise with the least per- 
ceptible breeze. Common especially N. 
2. P. grandidentata, Michx. LarGE-rooTHED Popriar. A tree 
60 to 80 ft. high, with rather smooth gray bark ; leaves 3-5 in. long, 
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 somewhat flattened, but not nearly as 
much so as that of the preceding species. Rich woods N. 
3. P. heterophylla, L. Swamp Popriar. Branches only slightly 
angled. Leaves ovate, mostly obtuse at the apex, rounded or sub- 
cordate at the base, serrate with obtuse teeth, densely woolly when 
