Comparative Study of the Secondary Xylem Vessel Elements in the Stems of Two Species of Rosa L Plants:Rosa multiflora var. multiflora,Rosa gallicaL.

Using vessel elements segregation technology and optical microscopy, a comparative study onRosa gallica L, Rosa multifloravar. multiflora in the Rosa L was conducted to find out about the statistics about their stem, secondary xylem of vessel type, quantity, length, diameter of vessel elements, perforation plate type and the tail characteristic. The results showed that: the vessel elements of the two types of plants mostly are chiefly pitted. Perforation plates are mostly single perfo- ration, and complex perforation and side wall perforation are also seen. The secondary wall holes are in the form of cross col- umn or a combination of both cross column and the column type. Most of the vessel elements are found to have branched tertia- ry thickening and tylosis exists is also seen in them. The vessel elements of the two fall into three types: two tailed ends, one single-tailed end, and two tailless ends. The two plants are of a relatively high degree of affinity, Rosa multifloravar. multiflo- ra is more advanced thanRosa gallica L in terms of evolution. But there are primitive characters in these two kinds of plants, and there are more primitive traits in whether different vessel elements or in the same vessel elements, indicating thatRosa gal- lica L and Rosa multifloravar. multiflora are of a higher position in the evolution system, but their properties are not synchro- nized in the evolution of the system, the ontogenetic development is just a repeated process of system development, thus dis- playing a different evolutionary relationship.