HELIOTROPISM OF THE STIPE 121 



The Heliotropic Effect of Light.— When the young fruit-bodies 

 in one of the crystalHsing-dish cultures had grown up so as almost 

 to touch the covering glass plate, the plate was removed and the 

 open dish was set in a large chamber having glass sides, a glass top, 

 and a zinc base (length, breadth, and height of the chamber respect- 

 ively 42, 21, and 26 inches), the air of which was maintained in a 

 sufficiently moist condition. The chamber was situated on a table 

 about 10 feet from a window facing the open toward the west. 

 Under these conditions the fruit-bodies expanded and shed their 

 spores in a perfectly normal manner. As the fruit-bodies developed, 

 they were subjected to unilateral window-light directed downwards 

 to them at an angle of about 70° with the vertical. 



In response to the unilateral illumination, each fruit-body, 

 during its development, sloped its axis from the vertical slightly 

 toward the source of light. The actual angles of slope for four 

 fruit-bodies were 15°, 10°, 10°, and 8° respectively. Numerous 

 observations of this kind made it evident that the stipes of Coprinus 

 sterquilinus are sUghtly heliotropic when illuminated with unilateral 

 Hght. A few experiments confirmed this deduction. In one of 

 these, the dish containing a very young fruit-body, not quite one 

 inch high, was turned round, so that the axis of the stipe was set 

 at a slope of 16° from the vertical in a direction away from a window 

 (Fig. 69, B). After 24 hours, owing to growth, the axis of the stipe 

 had come to slope 8° toward the source of the light (Fig. 69, C), so 

 that a heliotropic curvature of 24° had taken place. This slope 

 toward the direction of the incident light-rays was maintained 

 in the lower two-thirds of the stipe during the further elongation 

 of the stipe and even during the expansion of the pileus (Fig. 69, D). 



seems probable that the flagstone was actually raised by the fruit-bodies, as in the 

 cases recorded by Cooke and Carpenter, there is just the possibility that the primary 

 cause of the upheaval was a growing root upon which the fungus had vegetated, 

 for it is well known that growing roots do actually disturb paving stones as they 

 increase in thickness. There is no reason to doubt the general accuracy of the 

 observations here cited. If a small and relatively fragile Coprinus sterquilinus 

 fruit-body can exercise an upward pressure of about half a pound, several firm and 

 large non-Coprinus fruit-bodies, like those of Lentinus lepideus, acting together, 

 might well exert an upward pressure of many pounds and raise stones of considerable 

 weight. 



