The Equisetopsida emerged in the Upper Devonian (>370 mya), and Equisetum (horsetails) may be the oldest surviving vascular plant genus. Horsetails and the Poales are the only plants possessing the hemicellulose (1->3, 1->4)-b-d-glucan (MLG). Xue and Fry show that variation has occurred in MLG structure during horsetail diversification, and that E. bogotense (the earliest-diverging species) has MLG [...]