PLATE 5. 



1 and 2. A simple apparatus for detecting changes in tissue tensions in the leaf during wilting. In 



the experiment in progress when photographs were made the leaf had bent upward during 



a short interval (fig. 1). It then moved downward (fig. 2). The index was set at at 



the beginning of the experiment. 



3. Method of studying the effect of different degrees of relative humidity on transpiration, using 



vertical tube potometer. 

 4. Bell-jars and "olla" in place during experimentation upon Verbena ciliata. 



