36 RESEARCHES ON FUNGI 



movement caused by the projectile, the mass of the projectile was 

 found to be 0-011 mg. By weighing, the dry weight of the pro- 

 jectile was found to be 0-0057 mg. The force of the discharge was 

 calculated to be 10-8 ergs or 26 x 10"^ calories. 



Pilobolus in its Relations with Light. — The response of Pilo- 

 bolus to light has been studied by Sorokin (1873), Fischer von 

 Waldheim (1875), Brefeld (1881), Regel (1881), Allen and Jolivette 

 (1914), Parr (1918), BuUer (1921), Pringsheim and Czurda (1927), 

 and Van der Wey (1929). 



The Effect of Light on Fruit-body Development. — Brefeld,^ for 

 Pilobolus crystallinus (his P. microsporus), found : (1) that, in the 

 absence of light, no sporangia are formed but the sporangiophores 

 continue to grow for 10-14 days until they become 8-10 inches long, 

 when they wither ; (2) that a two-hour exposure to light is sufficient 

 to cause a rudiment of a fruit-body to complete its development 

 in the dark ; and (3) that the fruit-bodies develop normally in blue 

 light but cannot develop their sporangia in red-yellow light. There 

 can be no doubt, therefore, that light stimulates P. crystallinus in 

 a formative or morphogenic manner. 



The Heliotropic Response of the Fruit-body to Light of Various 

 Colours. — The sporangiophores of Pilobolus exhibit marked helio- 

 tropism {cf. Fig. 13). Sorokin ^ Fischer, ^ and Brefeld studied the 

 heliotropic effect of light passed through (1) a solution of potassium 

 bichromate and (2) an ammoniacal solution of copper oxide. The 

 results were divergent. Sorokin found that Pilobolus gives no 

 hehotropic reaction in blue light and is negatively heliotropic in 

 red-yellow light, while Fischer obtained a strong positive response 

 in blue light but no response in red-yellow light. Subsequent work 

 has shown that these conclusions were erroneous. 



Brefeld ^ obtained a positive response in both blue and red- 



1 O. Brefeld, Untersuchungen iiber Schimmelpilze, Leipzig, Heft IV, 1881, 

 pp. 76-78 ; Heft VIII, 1889, p. 276, Taf. XII, Figs. 1-6. 



" N. Sorokin, " Ueber die Wirkung des Lichtes auf die Filze,'" Be ildge zu d. Proto- 

 collen der Sitz. d. Naturf.-Ges. an d. Univers. z. Kasan, 1875 (in Russian, cited from 

 Parr's paper). 



^ A. Fischer von Waldheim, " Ueber den Heliotropismus niederer Pilze," Arh. d. 

 hot. Lab. d. k. Univ. Warschau, Warschau, 1875, Heft I {vide Just's Bot. Jahresbericht, 

 Vol. Ill, 1875). 



* 0. Brefeld, loc. ciL, Heft IV, p. 77. 



