Incoming correspondence to George Engelmann from Frédéric Albert Constantin Weber, for 1866-1883. The correspondence relates to cacti found along expedition in Mexico stating that no new species had been found that were not already described by Engelmann. Descriptions, discussions and lists of Opuntia, Mammillaria, Echinocactus, Cereus, Agave, and various plants. Weber had prematurately returned from Mexican expedition to France and reassigned as principal physician in the garrison at Ouverrez. Many genera incorrectly used. Thorough discourse on several plants illustrating difficulty with definition of genders* and subgenders and agrees with Engelmann to reject the characteristic of the possible emergence of the ovary as a mediocre classification and as a genetic characteristic. States "Memoirs of Poselger in 1853" a very useful reference. Time has come for a scientific commission to be organized in Paris for the exploration of Mexico States full notes of Mammillaria micromeris. Disagreement with theory that variations of cacti in their homeland developed from hybridization. Invitation for first meeting with Engelmann in Paris. Request to be able to correspond with Engelmann concerning Weber's observations of cacti, having found large numbers of unedited documents on certain species. Request to redo Pfersdorff Catalog. Illness of three-year old son, descriptions in Engelmann's last letter. Encourages Engelmann to publish paper on cacti. Comments on veritble pillage that occurs in some botanical gardens.

Incoming correspondence to anonymous from Frédéric Albert Constantin Weber, for 1869. The correspondence relates to Francisco A. Sauvalle's address. Weber's address.

Incoming correspondence to German Hoppenstadt from Frédéric Albert Constantin Weber, for 1868. The correspondence relates to plans to publish research from a Mexico expedition. Discussion of organo, Cereus and Pilocereus.

Incoming correspondence to Frédéric Albert Constantin Weber from German Hoppenstedt, for 1868-1869. The correspondence relates to a discussion of Pilocereus and Cereus. Medical issues. Cacti seeds. State of affairs in Mexico. Hoppenstedt's family.

Incoming correspondence to Frédéric Albert Constantin Weber from Heinrich Poselger, for 1868-1869. The correspondence relates to classification of various cactus species. Variety of cacti confirms Darwin's theory.

Incoming correspondence to Frédéric Albert Constantin Weber from George Engelmann, for 1865-1883. The correspondence relates to a discussion of cacti, Cereus, Agave, Yucca. Exchange and publication of articles. A request for biographical information on Weber. Biographical information about Engelmann. Various travel plans. Various personal issues to Engelmann and family.

Folder contains original letters.