Cather had been using the word queer often in her book and it was to let out her and her character's secret, the truth. Throughout flowers bring him joy and relax him. Carnations are the major representation of Paul's life, but not giving the reason for having such a life. He put the violets and jonquils on the taboret beside the couch, and threw himself down, with a long sigh, covering himself with a Roman blanket. The herbal properties of the Violet help in many ways.
Violets are know for their calming ability.
Perhaps the sight of violets and the touch relax Paul, who was constantly described as a nervous character. John Calvin was the head organizer of the Calvinist religious group. This religion believed in predestination. Since Paul had a picture hanging on the wall over the head of his bead, we can assume his family believe in this doctrine. Remember he only speaks negative of it.