Figure 1. The relationship between number of fronds per rootstock in 1993 vs. 1994. Frequency values are the number of occurrences in each category (e.g. between 13 - 15 rootstocks had 4 fronds in 1993 and 3 in 1994). Only rootstocks that were sterile in both 1993 and 1994 are included (n = 192).