Abstract: This paper deals with comparative anatomy of nutritive organs of 12 species of the genera Thladiantha,Baijiania ane Momordica.The conclusions are as follows: 1.On the structure of tendrils, the differences between Thladiantha and baijiania are evident.The former has the perivascular fibers and the vascular bundles developed weakly; and on the other hand,in the latter there is no perivascular fibers ar all and the pvascular bundles well developed.It is considered that a completed vascular system is stronger than the perivascular fibers for the mechanical function of plants in Cucurbitaceae.2.Crystals, silica cells andcystoliths are respectively present in the plants of Baijiania, Siraitia and Momordica, but they are not found in Thladiantha.3.The evidence of comparative anatomy suggests that Thladiantha is closely related to Baijiania,but the latter is more advanced than the former in phylogeny.