BAYBERRY FAMILY 51 



or very coarsely toothed, densely white-downy beneath. Cultivated 

 as a shade tree and sometimes found growing spontaneously. 



2. P. tremuloides Michx. AMERICAN ASPEN, QUAKING ASP. A 

 tree 20-60 ft. high, with greenish-white bark. Leaves roundish, 

 heart-shaped, abruptly pointed, with small regular teeth. Leafstalk 

 long, slender, and flattened at right angles to the broad surfaces of 

 the leaf, causing it to sway edgewise with the least perceptible 

 breeze. Common especially N. 



3. P. grandidentata Michx. LARGE-TOOTHED POPLAR. A tree 

 60-80 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. 



4. P. heterophylla L. SWAMP POPLAR. 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 

 young, but becoming smooth with age ; petioles cylindrical. Pistil- 

 late catkins smooth, erect or spreading, loosely flowered. Capsule 

 ovoid, usually shorter than the pedicel. Common in river swamps. 

 A large tree with soft light wood, which is often used in making 

 cheap furniture.* 



5. P. deltoides Marsh. COTTONWOOD. A large and very rapidly 

 growing tree, 75-100 ft. or more high, often with a markedly excur- 

 rent trunk. Leaves large and broadly triangular, with crenate-serrate 

 margins and long, tapering, acute tips ; petioles long and considera- 

 bly flattened. The numerous pediceled capsules are quite conspicu- 

 ous when mature, and the air is filled with the downy seeds at the 

 time when the capsules open. Common W., especially along streams, 

 and planted as a shade tree. 



15. MYRICACEJE. BAYBERRY FAMILY 



Shrubs with alternate, simple, resinous-dotted leaves ; monos- 

 cious or dioecious. Flowers in short, bracted catkins ; perianth 

 none. Staminate flowers 2-10, stamens hypogynous ; pistillate 

 flowers surrounded by 2-6 scales. Ovary 1-celled ; style short ; 



stigmas 2. 



I. MYRICA L. 



Shrubs or small trees with the branches clustered at the 

 end of the growth of the previous season. Leaves short- 

 petioled, entire, lobed or toothed, the margin usually revolute, 



