In the poem, "the moss on the steps is green, and the grass in the curtain is green", and "moss" refers to _ _ _ _ plants, so it can be judged that this step must be in the _ _ _ _ ring.

Bryophytes have no true roots, only false roots, which only play a fixing role. Generally, there are stems and leaves, but there is no conducting tissue in the stems and leaves, so the plants are shorter. Bryophytes mostly live in humid environment, such as wet ground and shady walls, and they often grow densely, just like furry green carpets. As can be seen from the above, the plant "moss" that makes the steps green in the poem should be bryophytes, and this step must be among them.

So the answer is: moss; dank