Powers describes the general characteristics of the lavas of Kilauea and of Mauna Loa. The deeply-dissected volcanoes of the Hawaiian Islands consist of a foundation of olivine basalts like those of Kilauea, overlain by flows of variable composition, including trachyte and nepheline basalt. Basalt is the primary magma. The undifferentiated lavas contain no true phenocrysts of pyroxene, and the groundmass pyroxene is pigeonite. Differentiated lavas contain many pyroxene phenocrysts, which are characteristically diopside, and groundmass pyroxene is more commonly diopside than pigeonite. In the differentiated lavas, there is a more or less continuous precipitation of pyroxenes passing from diopside toward hedenbergite. Separation of the phenocrysts known to form in Hawaiian lavas cannot change the primitive basalts to differentiated types undersaturated in silica; hence, fractional crystallization alone is inadequate to explain the differentiation. This paper was written to offer a field perspective on some of the conclusions reached by Barth (1931a, b). The author quotes Cross (1915) and Sidney Powers (1920), with whose conclusions he is in agreement. The author draws three conclusions that differ from those of Barth: (1) diopside phenocrysts do not form in primary basaltic magma; (2) the changes in ferromagnesian content during differentiation of primary magma is not consistent with progression from diopsodic to hypersthenic pyroxenes; and (3) orthorhombic pyroxene should not be omitted from the sequence of pyroxenes in basalts.