On the cover: cover: Gunnera is the only angiosperm that hosts the symbiotic cyanobacterium Nostoc. Shown are the first red stem glands of a Gunnera manicata seedling. The glands, which are the sites of infection by Nostoc, develop independent of the presence of cyanobacteria. Vast amounts of a viscous mucilage are secreted from the glands and induce the differentiation of a motile life stage as well as the synthesis of specific proteins in compatible Nostoc. For the article by Rasmussen et al., see page 696.
