This sub-series contains glass plate negatives with views of crops, groves, orchards, buildings, and the original Citrus Experiment Station (CES) laboratory located on Mt. Rubidoux. Other images pertain to fieldwork and experiments conducted by CES staff and students. Images created or collected by E.E. Thomas depict orange and lemon trees, and alfalfa, barley, Hubam clover, and cowpea fields. Images pertaining to experiments with Eureka lemon, marsh grapefruit, Valencia orange, and Washington navel orange trees are also included.

For black-and-white photographs created or collected by E.E. Thomas, please consult Sub-series 8.2, Black-and-white photographs.