Hierarchical cluster analysis of flax EST libraries. Three gene expression clusters were identified, viz., early differentiating seed tissues, maturing embryos and juvenile vegetative tissues. The tree shows hierarchical clustering of the tissue-based libraries based on similarity/distance as measured by the Pearson correlation coefficient. Values close to 1 have high degree of similarity whereas lower values indicate the degree of distance between two libraries. Globular embryo (GE), heart embryo (HE), torpedo embryo (TE), cotyledon embryo (CE), mature embryo (ME), globular stage seed coat (GC), torpedo stage seed coat (TC), pooled endosperm (EN), etiolated seedlings (ES), stem (ST), stem peel (PS), leaves (LF), and mature flower (FL).