POPLAR. 261 
Plate 22. Populus tremuloides. Aspen. 
1. Flowering branch of staminate tree, one-half natural size. 2. Flow- 
ering branch of pistillate tree, one-half natural size. 3. Scale of staminate 
catkin, enlarged. 4. Stamen, enlarged. 5. Scale of pistillate catkin, en- 
larged. 6. Longitudinal section of pistil. 7. Mature fruit, natural size. 8. 
Fruit, showing mode of dehiscence, natural size. 9. Seed, enlarged. 1o. 
Longitudinal section of seed, enlarged. 11. Imbryo, enlarged. 12, Fruit- 
ing branch, one-half natural size, 
