| Abstract: | The family Cephalotaxaceae contains only one genus, Cephalotaxus, with 9 species and some varieties, mostly endemic to China. The present paper deals with the comparative anatomy of secondary phloem of stems in 4species and I cultivar, of this genus under light microscope and scanning electron microscope.The main results are as follows: (1) The structure of secondary phloem is rather uniform in the various species of thisgenus. In cross section, sieve cells, phloem parenchyma cells form continuous tangential rowsof one cell in width respectively, which occur alternately. Sclerenchyma cells also form continuous tangential rows, each with a radial width of 1-4 cells. The interval between the rowsis rather wide. (2) The type of phloem fiber and the quantity of sclereids can be served as the characters for identification of species and the evidence for the separation of two sections of Cephalotaxus, namely: Cephalotaxus and Pectinatae. (3) The secondary phloem of this genus contains more or less crystalliferous parenchymacells, in the inner tangential walls of which calcium oxalate crystals are embedded. So far thischaracter has not been reported in the other families and the genera of conifers. Our conclusion, therefore, agrees with the opinion that Cephalotaxaceae is a natural taxon and includesonly one genus, Cephalotaxus. |
