PO_REF:00003

H.P.J. Robbertse, N. Grobbelaar, and E. du Toit, 2011. Origin of the Coleorhiza in Cycad Seedlings and its Structural Homology with That of the Poaceae. The Botanical Review 77(1):1-10
DOI: 10.1007/s12229-010-9058-4
link to article