74 RESEARCHES ON FUNGI 



time are plotted out in Fig. 28. The resulting curve is one of 

 damped oscillations, roughly resembling that of a pendulum swing- 

 ing in a viscous medium. Some of the results plotted do not lie 

 on the curve. I have reason to suppose that this is due not to 

 irregularities of growth, but to errors in making the observations. 

 Greater accuracy, doubtless, would have been obtained if an assistant 

 had recorded times whilst I recorded angles, but, unfortunately, in 

 the absence of help, it was necessary for me to make the two sets 

 of measurements by myself. Both alertness and correctness of 

 judgment are required in order to place a sliding lever parallel to 

 the pileus plane. Practice, however, enables one to make the 

 necessary readings with considerable precision. 



In the development of the fruit-bodies in my laboratory an 

 undoubted periodicity was observed. A few fruit-bodies expanded 

 each morning and shed their spores during the mid-day hours, 

 usually between 12 and 3 o'clock. In properly cared for cultures I 

 could never find fruit-bodies opened at night. Successive crops 

 of mature fruit-bodies were thus produced with a diurnal rhythm. 

 A similar rhythm is well-known for Pilobolus ; and in Ascobolus 

 a few asci ripen and burst each day. The stretching of the spor- 

 angiophore of Pilobolus, and of a group of asci in Ascobolus, is 

 put off until morning, so that light may be used to direct the 

 growth of these heliotropic structures toward an open space. If 

 the orientation of the fungus guns were to take place at night, its 

 successful accomplishment would be simply a matter of chance. 

 In Coprinus plicatiloidcs the stipe is too massive a structure to 

 be fully developed in one morning. Its partial elongation and 

 curvature toward an open space in response to the stimulus of 

 light, take place on the day previous to spore-discharge. On the 

 next morning it erects the pileus in response to the stimulus of 

 gravity. It is clearly of advantage that the stipe shall begin to 

 elongate in the daytime rather than at night, for the first requisite 

 for the successful functioning of a fruit-body is that the pileus 

 shall be brought into the open. The rhythmic development of 

 the fruit-bodies of all the three coprophilous fungi seems, there- 

 fore, to be of distinct importance in facilitating the scattering of 

 the spores. 



