Both men are initially presented as similar in that both serve as mentors to Dave and both are convinced of the correctness of their position and ignorant of the valid reasons for taking another stance. Because advancing his education is important to Dave, he does not stand up to Professor Herbert and so he lets his father down. However, when his father comes to school and sees for himself some of the things Dave is learning, both he and the teacher eventually recognize important points about the others’ position. As befits their different professions, the professor wears a suit, while the father wears overalls.
Professor Herbert wants the students to broaden their horizons and he believes that he is relating to their environment through field trips. He sees nature as an object of study rather than as a means of providing livelihood. While he promotes the class and laboratory settings as the primary locations of learning, he also wants the students to see where the material comes from that they study in school. Luster Sexton, in contrast, is a farmer who evaluates each aspect of the environment in terms of its productive capacity. This extends to his understanding of the value of a dollar, in terms of exactly how much work it takes for him and his family to earn one. He sees the professor as not just clueless but discriminating against the poor by making his son work. He also belies that school is what you learn in the classroom, and objects to the teacher doing what he sees as wasting time on field trips.
When the two men meet, the differences are obvious but it is clear that they both place a high value on Dave’s welfare. Prof. Herbert is able to show Luster the relationship between practical and book-learning, and he begins to understand the financial situation that farmers face.