Populus tremuloides (quaking aspen) Laterally compressed petioles allow any breeze to cause leaves to vibrate or "quake". This movement makes it difficult for insects to land on or crawl on leaf surfaces.
Populus deltoides higher magnification of adaxial surface of stipular bud scale. Dark cells are resin-secreting epidermis, light line above epidermis is cuticle pushed off by secretory product.