  We have analysed 16 observations of class beta of GRS 1915+105 performed with
the Rossi X-ray Timing Explorer. We show the time-resolved evolution (every 16
seconds) of the X-ray spectral parameters during these observations. The three
model independent states (A, B, C) identified in the color-color diagrams are
described here in terms of the more physical (and model dependent) quantities
of the disc and power law components. As in the color analysis, we observe
specific and time-asymmetric transitions between states. Within a single
observation, we identified a loop-like cycle of the power law spectral index
that starts and ends with the ending of state C. There is evidence of local
mass accretion rate variations and mass loss during the long instability
intervals (long state C). This is consistent with simultaneous radio and X-ray
observations that show a one-to-one relation between the long state C and the
radio flares, that occur shortly after it: a loss of disc mass is followed by
an ejection of matter in the jet.
