Parr.—The Response of Pilobolus to Light . 195 
than in those of the Nernst. Further discussion of the energy relation will 
be taken up later. 
If the presentation periods be plotted with reference to frequency of the 
light waves in the spectral regions to which Pilobolus was exposed, the 
results will appear as in Fig. 4. These graphs are based on the data given 
Fig. 3. Graphs (from data in Tables IV, V, VI, and VII) in which abscissae represent the 
presentation time of Pilobolus and ordinates the energy values of the spectral regions to which the 
plant was exposed. 
in Tables II, VI, and VII. In this instance it will be noted that response 
in Pilobolus takes place in every region of the spectrum, and that the 
presentation period decreases from red to violet, or conversely, that the 
irritability increases from red to violet. These results then confirm those 
obtained by Brefeld (1881, p. 60) and Grantz (1898), and are contrary to 
those of Sorokin (1874) and of Fischer von Waldheim (1875). 
The graphs as given in Fig. 4 are remarkably constant in their gradual 
