“There was a cactus with bushy arms and a coat of yellow spines as thick as fur. A bird had built her nest in it...” What is being compared? What do the beings have in common?

Taylor is thinking this as she is at the doctor with Turtle. Turtle had gotten X-rays to possibly determine and give Taylor some kind of clue as to what might have happened to her before she had ended up with Turtle. The doctor puts the X-rays up in the window and has he explaining the picture to her she looks past it to see the garden on the other side. Maybe Taylor uses the bird with the nest in the cactus as possibly a reflection upon her and Turtle and how they have ended up. Althought Taylor ended up with Turtle very unexpectedly she never once hesitated giving her away or not taking a responsiblity, and how easily Turtle had made a home and comfort and trust in Taylor.