Polypody ferns and ceremony

On the northeast slope of North Manoosnoc in Leominster I stopped to take a picture of one of my favorite ferns: the polypody which Thoreau called "cheerful little communities". They often grow out from between the rocks like this:

So I was admiring the outcrops, seeing a few things here and there that looked arranged, and sat down to enjoy the place. I was sitting right on top of one arrangement:

See how the entire crack has been stuffed with smaller fragments? 
Looking a little further down the rock, I noticed something else behind the next group of ferns.

A closeup:

[See Manitou p 275,300 for discussion of buckets and historic period ceremonialism.]
I have long thought this part of Leominster - called "Notown" - must have been where the Indians of Fitchburg were displaced to, when the Europeans arrived. Since the area is full of large stone mounds I believe it must have been an important center, even before the historic period. And now I see Notown is likely to have been all one and the same place - from the past into the historic. It was abandoned only recently and polypody grow there now.