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Foresight studies are regularly conducted at sectoral or geographical scales, in order to help policy makers and economic actors to define their strategy of adaptation to climate change (CC).

Bolboschoenus maritimus is one of the major weed constraints for irrigated rice‐cropping systems in the Camargue, France. This perennial plant propagates mainly through the production of numerous tubers. Observations in both controlled conditions and on‐field studies were used to enhance the level of knowledge of the biology, functioning and infestation dynamics of B. maritimus, with a view to rationalize weed control practices. It was found that B. maritimus displayed a great potential to produce a large number of shoots, rhizomes and tubers. Its propagation in the field plots depended on the initial weed density and its spatial colonization did not show any preferred direction (isotropic). Further observations that were made in the paddy fields showed an interaction between the different cultural practices that were tested and the infestation dynamics of B. maritimus. Efficient control of B. maritimus infestation in the field should make use of the data reported here, based on three levels: (i) prevention of weed stem proliferation during the cropping season with specific herbicides; (ii) elimination of the tubers after the rice crop; and (iii) reduction of the tuber‐germinating ability.

NOTES 1009rigorous purification the m. p. can be raised to 88-89'. On catalytic hydrogenation the alcohol absorbs 0.9-1.0 mole of hydrogen.' Three grams of a non-alcoholic liquid were recovered from the volatile fraction obtained during the above ethyl borate treatment. The substance polymerized very rapidly on heating and this property, together with the rotation, refractive index, and method of preparation, indicates that it was probably impure carvopinone.8 (6) Jbshel, Hall and Palkin, I n d . Eng. Chcm., Anal. E d . , 18; 447 (1941).The preparation of ytterbium amalgam by the electrolytic method described earlier1 has been repeated, using a larger amount (4 g. of oxide) of the same starting material. The electrolyses were carried to the point where no further amalgam formation took place. The rare earths from amalgams and from residual electrolytes were then extracted as chlorides called I and 11, respectively. Chloride I formed much the larger part of the material; chloride I1 amounted to about 0.1 g.From chlorides I and I1 spectrograms were made using a replica grating of 15,000 lines per inch (5906 lines per cm.) and a graphite arc source.These spectrograms for the region 2500 to 4600 k., accompanied by that of iron, were enlarged photographically to give prints with a dispersion of one k. per mm. The enlarged prints were examined with the aid of Massachusetts Institute of Technology wave length tables2 and more than 250 of the strong lines identified.The spectrogram of chloride I was that of ytterbium containing a much smaller proportion of europium. No lines of other rare earths could be found on this spectrogram. That of chloride I1 showed in addition to some remaining ytterbium and europium, the presence of gadolinium, terbium, dysprosium, yttrium, erbium, thulium and lutecium. The presence of holmium was probable but could not be established with certainty because its strong lines were masked by those of other elements present.