MLA

Hayward & Muzzall, Hayward, E. J., b. 1838. Pampas grass. Box 18 | Folder : Hayward & Muzzall. undated. https://collections.library.yale.edu/catalog/10466771.

APA, 6th edition

Hayward & Muzzall, & Hayward, E. J., b. 1838. (["Box 18 | Folder : Hayward & Muzzall"])(undated)[Pampas grass]. https://collections.library.yale.edu/catalog/10466771.