About a third of the pictures in B.O.W. originally belonged in four series, and are best understood as parts of a series. The rest come under Abstract and Miscellaneous and stand alone.
The series may be found under the Categories menu on the right side, or by clicking on the Menu above the header. They are:
Some other pictures of trees,which are not in the Tree as Symbol series, are under Miscellaneous
Mandalas, tho not actually a series, also have a “category” since there are quite a few.