The distribution of dry matter and nitrogen in the potato tuber Variety : King Edward

1. The percentage of dry matter in the potato tuber is lowest in the skin and increases to the inner cortical layer, the zone containing the greater part of the vascular system, and decreases towards the centre of the tuber.2. In each zone the proportion of dry matter is higher towards the umbilical than the terminal end of the tuber.3. The percentage of nitrogen in the fresh material tends to decrease from the skin to the inner cortical layer and to increase in the medullary zone. Thus it increases from zone to zone in the opposite direction to the dry matter.4. Nitrogen tends to increase with dry matter from the terminal to the umbilical end.5. Microscopical examination shows the starch grains densest in the region of the vascular system, and decreasing towards the centre and surface of the tuber.6. A high degree of correlation is found between the specific gravity and percentage dry matter of whole tubers.7. For purposes of sampling the method of taking two radially opposed sectors, or two diagonally opposed eighths, was far more accurate than the coring method.