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Harvard University, Archives of the Gray Herbarium in repository 
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From:
Charles Robert Darwin
To:
Asa Gray
Date:
14 July [1862]
Source of text:
Gray Herbarium of Harvard University (70)
Summary:

Adaptations of orchid flowers. Believes the structure of all irregular flowers is adaptation to insect fertilisation.

Linum grandiflorum distinguishes its own pollen so that when placed on stigma of same flower the pollen-tube is not even exserted.

Contributor:
Darwin Correspondence Project