Discusses the theories, construction, operation, types, and advantages of fuel cells developed by the American space programs. Indicates that the cell is an ideal small-scale power source characterized by its compactness, high efficiency, reliability, and freedom from polluting fumes. (CC)

Describes several simple and inexpensive experiments designed to facilitate the study of normal and abnormal morphogenesis in the biology laboratory. Seedlings of the common garden pea are used in the experiments, and abnormal morphogenesis (tumors) are induced by a virulent strain of the crown-gall organism, Agrobacterium tumefaciens. (JR)

Discusses the use of a computer program to describe chemical reactions by the concepts of reaction coordinate and energy profile. Indicates that representation of a collision encounter by a trajectory on the energy surface leads to a precise explanation, rather than schematic, in the teaching chemical kinetics. (CC)

Discusses three possible methods of thinking about the implications of the definitions of the Avogadro constant and number. Indicates that there is only one way to arrive at a simple and standard conclusion. (CC)