How does the description of the ivy vine in paragraph 18 contribute to the tone of the passage?

The description of the Ivy Vine in paragraph 18 shows Sue's determination to keep johnsy alive. It also reflects upon the pathetic environment where sue and johnsy live.

Explanation

The context of the above lines has been taken from the story named The Last Leaf written by O' Henry. This was published in 1907 in his work The Trimmed Lamp and another story. The backdrop of this story revolves around two characters Johnsy and Behrman who give each other consolation and reason to live and stay calm. The story is set at a village called Greenwich where people find themselves amid a pandemic called pneumonia. There is an old artist and painter named Behrman who give a fragile and dying person Johnsy reason to live and cheer up. He tries to make her determination stronger and gives her the courage to live against all odds. Johnsy keeps on counting the falling Ivy leaves since she thought that once the last leaf falls she is going to die, however, the contrary happens, Bhermn who was the painter standing in the rain and painting the leaf for her, had to die.