The tracheary elements of S. sanguinolenta and S. pulvinata were the most evolutionary, followed by S. davidii and that of S. sinensis was the most primitive in the four species of Selaginella.

• 这4种卷柏中，圆枝卷柏和垫状卷柏的管状分子最为进化，蔓出卷柏次之，中华卷柏最原始。