The average number of (1) antichains, (2) maximal antichains, (3) chains, (4) infima closed sets, (5) connected sets, (6) independent sets, (7) maximal independent sets, (8) brooms, (9) matchings, (10) maximal matchings, (11) linear extensions, and (12) drawings in (of) a rooted plane tree on n vertices is investigated. Using generating functions we determine the asymptotics and give some explicit formulae and identities. In conclusion we discuss the extremal values of the above quantities and pose some problems.

Remark:

There are some overlaps with other papers. See Addendum.