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Letter 11570

Darwin, C. R. to Darwin, Francis

26 June [1878]

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    Asks questions related to movement in plants. The cotyledons of Oxalis offer a promising field for study.

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    Wonders why Julius von Sachs thinks bloom is a protection against insects.

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    Encloses notes on the cotyledons of Oxalis species.


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[Enclosure: 1]

June 25th 1878. The short petioles of the Cots. of Cassia are enlarged, transversely wrinkled & formed of tissues appearing different from that of lamina & Hypocotyl.— How is Oxalis valdiviana & rosea or floribunda?? I neglected to observe with Cassia whether when Cots. Horizontal upper surface of petiole is transversely wrinkled.—

I have looked at Cots. of Oxalis floribunda & there seems to be a semicircular pale-coloured pulvinus on upper surface formed of smaller cells; but it tired me too much to look carefully.— Now on O. corniculata the cots of which raise only 45o I can see no pulvinus.— This very important showing that pulvinus developed in same genus.

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