Would like to borrow the pamphlet on variation [Frédéric Gérard, "De l’espèce dans les corps organisés" (1844), extract from Dictionnaire universel d’histoire naturelle, ed. C. D. d’Orbigny].
Glad to hear Humboldt’s views on migration. CD believes we cannot "put any limit to the possible and even probable migration of plants".
Wants good book on plant morphology.