False colour scanning electron micrograph of a section across a cut leaf petiole (stalk) of the water lily Nymphaea album. The water lily has overcome difficulty of getting air to its submerged roots by having large diameter open tubes within the leaf petiole. These hollow tubes are connected directly to large air spaces in the leaves, which contribute to the plant's bouyancy. The tubes are lined with epidermal cells & studded with branched trichomes (hairs, centre). Some tubes contain crystals of calcium oxalate (not seen). Their function is unknown. Oxalate is poisonous & may act as a deterrent to burrowing animals. Magnification: X6 at 35mm size. Original is BW print B725/112