Learning to sample from trees!

Larson, PR and JG Isebrands. 1971. The Plastochron Index as Applied to Developmental Studies of Cottonwood. Can. J. Forest Res. 1(1): 1-11.

I'm pretty sure this journal was made to publish this paper. Vol 1, Number 1, Page 1. It was a pretty good paper...

"... the PI [plastochron index] and LPI [lead plastochron index] can serve two useful purposes when applied to developmental sutdies of woody plants: (1) to adjust plants of different developmental stages to a standardized morphological time scale, and (2) to predict developmental processes and events from simple, nondestructive measurements."