ABSTRACT.-Pollen from adobe bricks of the historic Brockman house of Tucson, Arizona, provides clues to the construction history of the building. Seventeen pollen samples were obtained from two separate walls and the mortar joining the bricks of one wall. The chenoam pollen type is dominant in all samples, and its proportion and concentration are signifi· cantly different between the two walls as indicated by chi square contingency tests. Similar differences are seen in high spine Compositae, Ambrosia type, Gramineae, Leguminosae, Pinus and in the AP:NAP ratio. Salsola type pollen was differentiated from other cheno·am pollen in this study. It was present in all adobe brick but it was rare or absent in the clay rich mortar. The variability among three samples from a single adobe brick is not statistically significant. Chi square contingency tests indicate similarity between modern soil (S2) and the adobe of wall I. The adobe of wall II was distinctly different from the modem soil. Chi square contingency tests also indicate similarity in pollen content of mortar and wall n\ and significant differences between pollen content of mortar and wall I. Pollen content in~e adobe brick can be interpreted as indicating two building phases for the house. Historic\.records indicate the earliest construction postdated 1901. Therefore, Salsola invasion into :the area must predate 1901 based on this pollen evidence
