2.1 Plant material
We used the germplasm resources of the Arnold Arboretum of Harvard
University, which includes greenhouse-grown Austrobaileya
scandens plants ranging in age from 20 to ~ 25 years
old. The leaf area of seven terminal branches from different plants was
measured by photographing each opposite leaf pair from the branch tip to
the seventh node (total n=84 nodes), above which leaves reached the
maximum size.