Distribution and development of secretory ducts in Trichoscypha (Anacardiaceae)

Distribution and development of three different secretory ducts systems were studied in leaves, stems and roots of several Trichoscypha species (Anacardiaceae) from west tropical Africa. One primary three-dimensional network occurs in the pith and the cortex of the stem and mesophyll of the leaves. A second primary system of mainly longitudinal orientated, hardly ramifying, secretory ducts is found in the metaphloem of leaves, stem and roots while a secondary three-dimensional system is detected in the secondary phloem of leaves, stem and roots. In the stem and roots, the last system is continuous with the secondary xylem via horizontal secretory ducts in both secondary phloemand xylem rays. The three systems are separated from one another. Ducts initiate schizogenously and develop further lysigenously in the primary phloem of the root, in the secondary phloem of the stem and sometimes also in the wood rays. In other parts of the plant the ducts develop entirely lysigenously.