Table 7. Summary of characters, and for which Principal Component Axis they are most important, i.e., how large absolute values for measures are expressed on selected axes. "Low" indicates a negative loading coefficient, plotting low on the PCA axis, and "high" the opposite. Characters are ordered by their relative importance (absolute value of loading coefficients, Table 4) to among genera variation and are illustrated in Figure 2.

 
Character
Variation Among Genera
Variation Within Genera
 
Aperture Diameter (AD)
PCA-2 (low)
variable
 
PCA-3 (high)
 
PCA-5 (high)
 
Dissepiment Width (DW)
PCA-2 (low)
PCA-6 (high)
 
PCA-5 (low)
 
Aperture Along-Branch spacing (AAB)
PCA-2 (high)
PCA-8 (low)
 
Node Diameter (ND)
PCA-3 (high)
PCA-8 (high)
 
PCA-4 (high)
 
Fenestrule Length (FL)
PCA-3 (low)
PCA-9 (high)
 
Fenestrule Width (FW)
PCA-3 (low)
PCA-7 (low)
 
Node Spacing (NS)
PCA-3 (low)
PCA-7 (high)
 
PCA-9 (low)
 
Aperture Lateral
PCA-3 (high)
PCA-8 (high)
 
Spacing (ALB)
PCA-5 (high)
 
Branch Width (BW)
PCA-4 (low)
PCA-6 (low)