This plant may be regarded as anatomically the most primitive of the Medulloseae.
Garrod in 1876 and 1877 who finally divested the Family of these aliens, but until examples of some of the other genera have been anatomically examined it may not be safe to say that they all belong to the Pteroptochidae.
In a few cases the hydrom strand is continued into the cortex of the stem as a leaf-trace bundle (the anatomically demonstrable trace of the leaf in the stem).
A consideration of these facts emphasizes still more fully the view with which we set out, that all living substance is fundamentally, the same, though differentiated both anatomically and physiologically in many directions and in different degrees.
Again, the degree of differentiation is very slight anatomically, but delicate protoplasmic threads have been shown to extend through all cell-walls, connecting together all the protoplasts of a plant.
The foot of the higher apes, though often spoken of as a hand, is anatomically not such, but a prehensile foot.
On the whole, the anatomy of Sigillaria is closely related to that of the preceding group, and in fact a continuous series can be traced from the anatomically simplest species of Lepidodendron to the most modified Sigillariae.
The family Calamopityeae, allied anatomically to Lyginodendreae, is of Devonian and Lower Carboniferous age.
Anatomically the connexion of the family with the Pteridosperms (and through them, presumably, with some primitive group of Ferns) seems clear, but we have as yet no indications of the stages in the evolution of their reproductive organs.
It is thought to depend upon some connexion, not yet anatomically demonstrated, between the third cranial nerve and its nucleus in the floor of the iter and the substantia nigra.