Dear Sir,

My brother writing from Calcutta says: “The closing of the leaves of the sensitive plant and the dropping of the stalks is apparently for protection as when they are closed you can hardly distinguish the pl⁠⟨⁠ant⁠⟩⁠ on the brown earth, and i⁠⟨⁠t⁠⟩⁠ would clearly be an advantage to hide thus when attacked by a goat or locusts.¹ The closing of the leaves at night too would protect the plant from beetles & fireflies which play havoc with leave⁠⟨⁠s⁠⟩⁠ ⁠⟨⁠at⁠⟩⁠ night. I find ⁠⟨⁠ma⁠⟩⁠ny p⁠⟨⁠lants⁠⟩⁠ with ⁠⟨⁠lea⁠⟩⁠ves like the Sensitive plant (or Acacia) close them at night.²

My sensitive plant is not affected when touched or even roughly stroked with a blade of grass, nor was it affected when the grass was laid on & then lifted off.

There is a sensitive plant precisely like the ordinary one that grows ⁠⟨⁠i⁠⟩⁠n water—running along the surface. The leaves are larger, and the flower white & larger but in other respects the plants look the same.³ Strong shaking by our strong winds does not close the leaves of the water plant, but the land one closes slightly under the same ⁠⟨⁠ci⁠⟩⁠rcumstances.”

Three things str⁠⟨⁠u⁠⟩⁠ck me in my brothers remarks:

1. The difficulty of seeing the closed sensitive plant on the brown baked earth of India.

2. The multitude of night flying fireflies and insects found in India, from which a plant might find protection useful.

3. The fact of there being a water sensitive plant—which however may not be new to you.

Yours faithfully | J I Rogers.

F. Darwin Esq.