Chimeras and the Origin of Lateral Root Primordia in Zea mays

The difficulty of determining the contribution made by the pericycle and endodermis of mother roots to lateral primordia in the Gramineae has been solved by inducing polyploid chimeras at initiation. The endodermis forms a layer covering the primordium, but this layer does not form the epidermis of the lateral. It does form the root cap of the young primordium, but this is replaced at a variable stage of development by the quiescent centre donating a new set of cap initials of pericyclic origin. Reasons for the previous diversity of interpretations are presented.