Abstract: The comparative studies of the structure of secondary phloem in 7 species of 2 genera of Salicaceae is studied.The results showed:(1) Populus and Salix. in their anatomical structures of secondary phloem, exhibit some similar features:distinct stratification in the secondary phloem;phloem fibres and crystal-containing cells in tangential bands alternating with bands of sieve clements, companion cells and phloem parenchyma cells; and sieve elements with compound sieve plates and oblique end walls bearing 7 to 8 sieve areas.(2) There are obvious differences between them in type or ray cells and crystals. Sclereids were not found in secondary phloem in Salix. and they existed in non-conducting phloem of Populus. (3) Some phloem anatomical features of the two genera are more primitive in evolution.

Key words: Salicaceac, Sieve elements, Rays, Phloem anatomy, Crystals