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Pulvinus Nicotiana rustica? Oct 17

A young leaf 9cm long in a longitudinal section one sees a mass of small celled tissue on the underside of petiole close to the base. The cells are 8 × 20 & are arranged with long axis perpendic (HKV) to axis of leaf. The ordinary parenchyma cells have long axis parallel to axis of leaf are between 17 × 12 and 23 × 15

In the older leaf 14 cm the contrast between the pulvinus cells & others is not quite so evident partly because the ordinary parenchyma cells are squarer & also the pulvinus cells have grown though not very distinctly. The ordinary parenchyma cells are bigger than in the young leaf but the different layers vary much & I cannot give the difference in numbers. They are chiefly bigger by being thicker than the young cells, but are also longer some being 30 or 35 in length.