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Raghavan reports for the first time that vivipary can be induced in wild-type Arabidopsis thaliana by culturing siliques in a hormone-free sucrose-supplemented mineral salt medium. The author was able to obtain viviparous seedlings from siliques cultured at very early stages of embryo development in a culture system that could potentially prove useful for investigating aspects of both normal and defective embryogenesis in this model plant. In addition, the author has characterized the state of cell division in growing embryos of cultured siliques of a transgenic A. thaliana harboring the cyclin gene construct fused to the GUS (;rs-glucuronidase) reporter gene. (see p. 766)

Callose indigestion and microspore rotation

Tsou and Fu solve an interesting problem in aperture position in pollen of the Annonaceae, the largest family of primitive angiosperms, which produces monads, tetrads, and polyads. The palynology of this family has been considered highly important to understanding higher level relationships, but tetrad formation has only been studied in one species (Asimina triloba) previously. Using Annona glabra and Annona montana, the authors describe a number of unique pheonomena that have not been reported in the Annonaceae or elsewhere in the angiosperms. A partially digested callosic envelope, containing cellulose, holds the tetrad together until the microspores rotate out of the microspore chamber in succession. (see p.734)

Mysterious endosymbiont exits Gingko

Tissue-cultured cells of Gingko biloba have yielded a remarkable surprise=man intracellular algal symbiont, a cryptic trebouxiophyte (green alga) that only appears when Ginkgo tissues are cultured in vitro. In work that covers ten years of observation and a variety of techniques and tissues, Tr;aaemouillaux-Guiller et al. have excluded the possibility of exogenous contamination. The proliferation of the alga from parent Gingko cells is associated ultimately with host cell necrosis. The physical origin of the endosymbiont is unknown. (see p. 727)

Island broom biogeography

Percy and Cronk present the first extensive phylogenetic study of legumes endemic to the Macaronesian islands, in particular species of Teline, Genista, and Adenocarpus, which are endemic to the Canary Islands and Madeira. Molecular data, and superb maps, enhance their discussion of multiple introductions for congeneric species, vertical and horizontal colonization, and the taxonomic status of insular vs. continental relatives. Each of the three genera investigated has undergone a unique pattern of island diversification, showing the varying effects of ecological (within island) or geographical (between island) speciation. (see p. 854)

This Article Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Search for Related Content