Context: The structure of hardwoods is more complex. The water conducting capability is mostly taken care of by vessels: in some cases (oak, chestnut, ash) these are quite large and distinct, in others (buckeye, poplar, willow) too small to be seen without a hand lens. In discussing such woods it is customary to divide them into two large classes, ring-porous and diffuse-porous.

Question: Is the structure of hardwood simple or complex?
Answer: complex

Question: What handles most of the water conduction in hardwoods?
Answer: vessels

Question: Are the vessels in chestnut wood large or small?
Answer: large

Question: In wood from a willow tree, what would you need to use to see the tiny vessels?
Answer: a hand lens

Question: Besides ring-porous, what's the other class hardwoods are often divided into?
Answer: diffuse-porous