Emission spectra of laser-produced plasmas on targets of Cs, Ba and the lanthanides have been studied systematically in the region from 40 - 300Å. In the lighter of these elements the most characteristic feature is a strong emission maximum consisting of a mixture of continuum and discrete lines. The maximum is centered at 102 Å for cesium and moves to shorter wavelength with increasing Z. At praeseodymium a second maximum appears at longer wavelengths and with increasing Z both maxima broaden and eventually form a single continuum. The resonances are interpreted as excitation of 4d10 4fN9 to 4d 4fN+1 followed by re-emission modified by the presence of the exciting electron. The extensive continua which appear with the progressive filling of the f shell, are attributed to brehmstrahlung radiation.