Although each succeeding week now shows very little change in experiment-to-date CO2 concentrations or in growth parameter vs. CO2 relationships, the absolute values of the parameters we measure each week continue to rise.  And some of these numbers are interesting in their own right.  Total root length per plant in Tanks 1 and 2, for example, averages only 7 cm.  But in Tanks 3 and 4 it averages 65 cm; and in Tanks 5 and 6 it averages 88 cm.  And the latter number represents a lot of root for a little plant.