The older types of Gymnosperms are inelastic and dying out.
Companion cells are not found in the Pteridophyta and Gymnosperms. In the latter their place is taken by certain cells of the medullary rays and bast parenchyma.
As in other parts of the earth, the Triassic was the age of gymnosperms, which were represented by diverse types.
Brongniart, who was the first to investigate in detail the anatomy of a cycadean stem, recognized an agreement, as regards the secondary wood, with Dicotyledons and Gymnosperms, rather than with MonocoFIG.8.