17. What are the main plant
tissues that form the rings
observed on stem sections of
some trees?

Gap-fill exercise

Fill in all the gaps, then press "Check" to check your answers. Use the "Hint" button to get a free letter if an answer is giving you trouble. You can also click on the "[?]" button to get a clue. Note that you will lose points if you ask for hints or clues!
The rings observed on stem cross
section of trees are made of
tissues: xylem and phloem.