It’s an avocado, an aguacate, also known as an alligator pear in English and a “lawyer pear” in Dutch. This is a Taft variety, an ancestor of the Lula cultivar, and may or may not still be around. In the 1910s, it was a well-known summer variety of the “Guatemalan race” of avocados. There are three races of avocados, did you know? The one you probably find in your grocery, the Hass, is a cross between Guatemalan and Mexican races probably. No one’s really sure because the first seed came from, like restaurant scraps, but the genetics show it’s got DNA from both.
The painting was done by Royal Charles Steadman, a government avocado artist, whose botanical paintings can be found in the USDA Pomological Watercolors collection.