Early Stages of the Development of a Pinnate Leaf of the North American Umbel Oxypolis greenmannii

Longitudinal section through a leaf primordium (length: 80 µm); Lower picture to the left: progressing development (length: 130 µm). First sign of the beginning development of a leaflet primordium. c. In this stage, a periodic pattern of meristematic activities along the whole primordium can be recognized. The meristematic cells are smaller and consequently stained darker than the further developed cells. The pattern is vertical to the axis of the leaf primordium (length 500µm = ½ mm). d. Almost completely developed leaf primordium with a periodic pattern of the leaflet primordia (D. R. KAPLAN, 1975).