Chlorophyll formation in seven day old etiolated mung bean leaves was inhibited by CMU. The inhibition was reversed by feeding sucrose, or by leaving the cotyledons attached to the leaves. Photosynthesis appeared to contribute substrates for further chloroplast development soon after its commencement. When sucrose was fed in the presence of CMU at a range of light intensities, there was a distinct light induced promotion of chlorophyll formation at light intensities of 500–2000 lux. Treatment of the leaves with salicyl‐aldoxime, an inhibitor of cyclic photophosphorylation indicated that this process could play an important part in chloroplast development.

A pathogenic strain of infectious bursal disease virus has been purified by density gradient centrifugation, principally on sucrose and tartrate gradients. Examination of gradient peak fractions by electron microscopy has revealed two populations of particles of average size 62 nm and 20 nm, which band together on sucrose and tartrate gradients. Purified virus has been shown to reproduce the typical symptoms and lftsions of infectious bursal disease. The possible classification of the larger virus particle in the diplornavirus group and the origin of the smaller particle are discussed.