First, notice the cone-shaped items at the twig tips and in some instances along the twig sides. These are buds. Some buds contain next season's leaves and stems and others contain flowers. Buds terminating twigs are called terminal buds while buds arising along the stem are lateral buds. Below each bud you can see a variously-shaped leaf scar, where last year's leaf-petiole was attached. Inside the Sycamore's leaf scar you can barely see dot-like bundle scars resulting when the tiny tubes carrying water, nutrients and other substances from the main stem to the leaf broke as the leaf petiole snapped off the twig.
By now it may have occurred to you that if you pay attention to buds and leaf scars you should be able to identify trees and bushes in the winter, without the help of flowers, fruits and leaves! In fact, this can be lots of fun, but you'll need a hand lens! Here are some hints for identifying the twigs above:
The twig above is from a Hophornbeam tree near my home. The neat thing about it is that the twig was scanned in early spring as the buds were expanding. All winter the buds had been tiny and brown but now the bud contents and the bud scales around them are enlarging and turning green. You can still see the brown tips of the scales, which all winter were the only parts of the bud exposed to the cold temperatures.
Soon the buds will break open in a way similar to what is happening in these two pictures. The picture below and to the left shows a hickory tree's terminal bud (the bud terminating the stem) just beginning to release its leaves.The picture at the right shows how flowers of the American Elm emerge from a twig's flower buds. In that picture notice that the terminal bud is not yet open. It contains leaf and stem material, which will emerge later.
This bud-opening process is something magical that happens on limbs of deciduous trees every spring. To see it you just have to know some basic facts about stems and buds, and be paying attention...