Extinct plants

The extinct plants are Crotalaria, Changium smyrnioides, Swamp Orchid, China ancient fruit, seed fern, Starwood and so on. Changium smyrnioides is a perennial herb of Changium smyrnioides in Umbelliferae. The main root is spindle-shaped, the stem is erect, the height can reach 100 cm, it is cylindrical, branched, the basal leaves are at most, the stalk is long, and the leaves are wide and oval once. The total bracts are few, and the tips are gradually pointed; The umbel has flowers, which are white after opening. The terminal umbel is almost completely pregnant, the petals are oblong or ovoid-lanceolate, the anthers are ovoid, the base of the style is raised, the fruit is ovoid to ovoid-oblong, and the fruit margin is not obvious. It blooms in April.

Swamp orchid is a perennial herb. 5-20 cm long, with brown or yellowish surface and white inside. The stem is upright, 50- 100 cm high, cylindrical, and the surface is covered with white powder. There are branches, there are branches, and they spread out. Lateral branches are usually alternate, and the branchlets on the lateral branches are alternate or opposite. Basal leaves are from few to many, with long stalks, 3- 15 cm long; The triple pinna is oval or oval, with a length of 1-2 cm, a truncated or nearly wedge-shaped base, a 3-lobed edge or a pinnate notch, and the last lobe is oblong and lanceolate, with a length of 2-4 mm and a width of 1-2 mm; The leaves on the upper part of the stem shrink into scales or leaf sheaths.

Seed fern originated from gymnosperms and first appeared in the late Devonian. It flourished in Carboniferous and Permian, gradually declined in Mesozoic and died out in Cretaceous. Although the seed fern has seeds, it has no embryos; Although there are pollen grains, they can't bloom. All these characteristics show that seed fern is a primitive seed plant, and it can also show that seeds appear earlier than flowers and fruits in the process of plant development.