Compositae are comparatively rare; so also Gramineae and Cyperaceae are in some places deficient, and Labiatae, Leguminosae and ferns in others.
As the Gobi desert is approached the forests disappear, the ground becomes covered chiefly with dry Gramineae, and Salsolaceae make their appearance.
The most remarkable feature here is the class of Liorhizal Dicotyledons, which includes only the families of Nymphaeaceae and Gramineae.
It is based upon the fact that the histological differentiation of the epidermis of their root is that generally characteristic of Monocotyledons, whilst they have two cotyledons - the old view of the epiblast as a second cotyledon in Gramineae being adopted.
On the drier and higher mountains of the interior of the chain, the forests become more open, and are spread less uniformly over the hill-sides, a luxuriant herbaceous vegetation appears, and the number of shrubby Leguminosae, such as Desmodium and Indigofera, increases, as well as Ranunculaceae, Rosaceae, Umbelliferae, Labiatae, Gramineae, Cyperaceae and other European genera.