Equisetums have hardly changed since prehistoric times, when they formed a large part of the vegetation that decomposed to form coal seams.
(Equisetums; have hardly changed; T:since prehistoric times; T:when they formed a large part of the vegetation) (they; formed; a large part of the vegetation) (the vegetation; decomposed; ) (the vegetation; to form; coal seams)
Equisetums they the vegetation the vegetation
have hardly changed formed decomposed to form
T:since prehistoric times T:when they formed a large part of the vegetation
a large part of the vegetation
coal seams