Before revision:  {\it  {\it   Fitting with a linear behavior \alpha(T), we find evidence  for a decreasing growth rate as a function of T . However, a decrease in the growth rate is visible also in the very low-T data. Going beyond a linear model, a peak at about (9.5 2.6)^\circ C seems to be present in the data.
After revision:  {\it {\it Fitting with a linear behavior \alpha(T), we find evidence for a decreasing growth rate as a function of T  2.6)^\circ C seems to be present in the data.