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Windham and Yatskievych present important new chromosome number data for cheilanthoid ferns, which are components of desert floras on nearly every continent. Enhancing the value of the study are (1) corroborating counts for some previously counted taxa, (2) convincing arguments correcting errors and resolving conflicts in the literature for some of these taxa, and (3) a phylogenetic taxonomic context in which the distribution of available accurate numbers for the cheilanthoid ferns is interpreted and discussed. Much more than just a listing of new chromosome counts, this study advances our understanding of fern evolution. (see p. 1788)

Sphagnum roots

Shaw et al. establish a much-needed phylogenetic context for Sphagnum, by far the most economically and ecologically important genus of mosses. It is also one of the most diverse lineages. Not all members of the genus are peat forming and absorption powers vary. In order to find the origin of characters accounting for these attributes, a rooted phylogeny is required and Shaw et al.'s study will undoubtedly compose the reference for any future phylogenetic study of peatmosses. (see p. 1777)

The tree

Hilu et al. consider the use of sequences from rapidly evolving genes vs. slowly evolving genes in creating a deep-rooted angiosperm tree. The overall substitution rate of matK is much higher than that of other plastid genes traditionally preferred for deep-level phylogeny in plants, such as rbcL and atpB. Using 374 matK sequences, representing all angiosperm orders and 12 gymnosperm genera, yielded a more robust tree than those based on individual genes and comparable to those based on four to 11 genes combined. Their analysis provides an angiosperm tree based on the largest data set so far compiled for matK. In addition, they compare the results of their analyses with previous trees. (see front cover and p. 1758)

A single-cell C 4 system

Voznesenskaya et al. address a significant and fascinating problem, that of cellular differentiation in the unusual situation where two ends of the same cell carry out quite different functions. They describe a single-cell C₄ system in the leaves of Borszczowia aralocaspica (Chenopodiaceae), in which chlorenchyma cells are anatomically and biochemically polarized. Their integration of structural and physiological measures of differentiation is significant for understanding the problem of cell differentiation in general and the differentiation of the specialized anatomy that accompanies C₄ biochemistry in particular. (see p. 1669)

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