The distribution of green and yellow parts in the foliage of a mericlinal chimera suggested that there are six initial cells for layer 2 (L2) in potatoes. The L2 of leaves traces back to only two cells, resulting in some leaves which had green leaflets on one side and yellow on the other; other leaves were all green or all yellow. Layer 3 (L3) showed a behaviour similar to L2 in one year but in the following year a more complex pattern of sectors, leaves having light green as well as normal green and yellow parts, was found suggesting that cell divisions in L3 do not follow so regular a plan as do those in L2.