Following a study of various plant roots, observations indicate that in Sagittaria latijolia secondary roots have the same histogenic regions as other roots. The rootlet is probably initiated by a plate of pericyclic cells of which the central cell, and later the lateral cells, divide periclinally and then anticlinally. From this plate arises the plerome. The origin of the calyptrogen and dermatogen is discussed and the for-mation of air spaces.