Sampling is of vital importance in biogeochemical investigations. In particular:
(1) Only organs of the same age should be compared.
(2) Preferably that organ of a tree which responds best to the element being investigated should be selected.
(3) Second-year twigs give more reproducible results than do first-year twigs.
(4) Lower and top branches may not contain the same amounts of a metal.
(5) A few specific elements are concentrated in larger amounts in particular plants: where practicable the use of these accumulator plants simplifies operations and provides better contrast between normal and anomalous samples.
(6) Anomalies are better detected when results are expressed in p.p.m. of ash rather than of dry plant.
Analyses of plants collected on the property of the Graham Bosquet Mines near Vancouver, B. C. graphically illustrate some of the above points.