Final answer:
A tree doctor, known as an arborist or a dendrologist, specializes in identifying, treating, and caring for various tree species. The names of trees are crucial to their expertise, akin to a medical doctor's knowledge of human diseases.
Step-by-step explanation:
When we discuss a tree doctor and his use of twenty or more names of trees, we are referring to the expertise of an arborist or a dendrologist. These specialists have extensive knowledge about different species of trees, their characteristics, care, and the ecosystem in which they thrive. They are skilled in the diagnosis and treatment of tree diseases and pests, which is similar to a doctor who diagnoses and treats human ailments. Arborists often need to identify and be familiar with a wide variety of tree species, which is why knowledge of the names is essential in their field.