It's fair to say that the botany teacher is not very sympathetic towards the narrator. This, despite the fact that the narrator has incredibly bad eyesight and can't see down a microscope very well.
The botany teacher appears to have more understanding for what he sees when he peers down a microscope at the contents of a Petri dish than he does for his students. He seems to think that the narrator is just being lazy, when in actual fact, he has a genuine problem with his eyesight. It's ironic indeed that a scientist of all people should be unable to acknowledge the damaging effect that such ailments can have.
Nevertheless, the botany teacher persists in trying to get the narrator to see plant cells through the microscope, but all to no avail. The teacher tries everything he can to make his student see what's on the slide, and at each setback—of which there are many—he gets progressively angrier, frustrated by what he sees as the narrator's incompetence and stupidity.
When the narrator starts drawing what he sees through the microscope, his teacher initially thinks that he's finally managed to get through to him. But it turns out that he hasn't drawn a picture of plants cells at all; he's drawn the reflection of his eye, which is all he can see.