Imagine what we should feel when we saw the first lateral stem bearing off from the main one, or putting forth a leaf. How we should watch the leaf gradually unfolding its little graceful hand; then another, then another; then the main stalk rising and producing more; then one of them giving indications of astonishing novelty—a bud! then this mysterious bud gradually unfolding, like the leaf, amazing us, enchanting us, almost alarming us with delight, as if we knew not what enchantment were to ensue, till at length, in all its fairy beauty, and odorous voluptuousness, and mysterious elaboration of tender and living sculpture, shone forth—“The bright consummate flower! ”

摘自《美国语文》中学课文第3课 A Flower For the Window作者：Leigh Hunt

我把相关的句子从段落中提取出来（我没有把结构看错吧？）：

How we should watch【then this mysterious bud gradually unfolding, like the leaf, amazing us, enchanting us, almost alarming us with delight, as if we knew not what enchantment were to ensue, till at length, in all its fairy beauty, and odorous voluptuousness, and mysterious elaboration of tender and living sculpture, shone forth—“The bright consummate flower! ”】

请教专家老师，“amazing us, enchanting us, almost alarming us with delight,”是前面“ ... then this mysterious bud gradually unfolding, like the leaf,”的非限制性定语？伴随状语？还是仍然延续watch sth doing sth 的结构？为什么？非常感谢老师。