Photoacoustic Imaging and Spec-troscopy is a multiauthored reference book that presents an advanced series of disparate chapters on the mathematical foundations, instrumentation, and applications of photoacoustic and thermoa-coustic imaging. Lihong Wang, an eminent author, educator, scientist, and leader in the field of photoa-coustic imaging and spectroscopy, is the editor of this book. Clearly this field is extremely active as evidenced by the diversity, the scope, and the quality of the field's published literature. Nevertheless , I was surprised to read the back cover, which I think is overreaching with the claim that photoacoustics may make as dynamic a contribution to modern medicine as the discovery of the x ray once did. While this may be a "typical" overstatement by the publisher's marketing team, it should be noted that within one year of the discovery of x rays there were more than one thousand publications related to the topic. As the editor points out, the phenomenon of photoacous-tics, in its simplest nonimaging form, was first reported in the 1880s by Alexander Graham Bell. Bell constructed a device that he called the photophone as well as subsequent devices such as the spectrophone. Focused light was incident on a rotating thin disk that emitted sound, which was detected with a stethoscope. The resulting sound wave was time modulated by the rotation of the thin disk and the frequency of the sound was equal to the rotation frequency. The reference to this paper appears in Chap. 12 of the book Biomedical Optics, Principles and Imaging see book review in

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Extrapolation of measurements of water use by individual trees to that for a stand of trees is a critical step in linking plant physiology and hydrology. Limitations in sampling resources and variation in tree sizes within a stand necessitate the use of some scaling relationship. Further, to scale tree water use in space as well as time, the relationship must reflect the changing availabilities of energy and water supply. It is argued here that tree leaf area is the most appropriate covariate of water use to achieve this aim. However, empirical results show that the relationship is not always linear. A theory is developed, based on the concepts of hydrological equilibrium (sensu Nemani and Running, 1989) and ecological field theory (Walker et al., 1989) which accounts for (occasional) non-linear behaviour of the flux/ leaf area relationship in evergreen trees. A key feature of this theory is the notion of a non-linear, quasi-equilibrium reflecting plant water stress. An equation is derived from these concepts and a standard, explicit treatment of tree water use (Landsberg and McMurtrie, 1984), which is used to characterise this relationship. This equation has the form Q = aIA + bQc,Af. The theory is tested against field data and published reports on Eucalyptus tree water use.