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Euphorbia Development of Pulvinus

The upper petiole has 3 or 4 layers of sub-epidermal tissue elongated cells of with walls shining like collenchyma— This tissue dies away rather ends where the pallisade cells begin & where the leaf is bent here the chlorophyll cells form a mass of irregularly oval cells, ha intermediate between the chlorophyll cells of the petiole which are elongated in direction of axis of petiole, & the pallisade cells of the lamina which are elongated at rt angles to surface of leaf. (There is certainly no structure the least like a pulvinus & no definite difference in structure between the old (eg 16th leaf from bud) & the youngest— The cells in this region are if anything slightly bigger in the old leaf which is what one would expect if they grew like ordinary parenchyma cells & did not remain embryonic like pulvinus cells.

Tropaeolum— There is no trace of tissue the least resembling pulvinus cells or distinguishable from ordinary parenchyma cells. The cells close under the leaf certainly grew as they are 2 or 3 times the size of the corre-

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ponding cells in a young leaf. I measured them in a leaf 12 mm in diam & one 46 mm