HISTORY OF PILOBOLUS 45 



same manner as Van der Wey has done in his recent paper, and my 

 solution was included in an address on the heliotropism of Pilobolus 

 which I gave in Canada ^ and in the United States ^ in 1920 and in 

 England^ in 1921. The address was accompanied by lantern slides, 

 among which were the construction diagrams shown in Figs. 46, 47, 

 and 59 (pp. 91, 92, and 124). In my paper ^ on Pilobolus published 

 in 1921 I treated of the heliotropic reaction of the sporangiophore 

 to one beam of light only and, in the expectation of publishing a 

 much fuller account of the fungus in the near future, did not even 

 mention my solution of the two-beam problem. Since 1921 until 

 now I have published nothing further on Pilobolus. Thus Van der 

 Wey, through the publication of his excellent paper in 1929, has 

 rightly obtained the credit for being the first to solve the two-beam 

 problem. 



My own solution of the two-beam problem was written several 

 years before Van der Wey\s paper came into my hands, and I have 

 therefore included it without alteration in a section of the next 

 chapter. 



The Discharge of the Sporangium.— In 1932, Ingold,^ in a brief 

 paper on the sporangiophore of Pilobolus Kleiiiii, described the mode 

 of discharge of the sporangium. He rightly affirmed that the 

 columella is shot away with the sporangium and that a drop of cell- 

 sap is attached to the gelatinous side of the sporangium as this 

 travels through the air. However, he failed to account correctly 

 for the fact that a sporangium becomes attached by its gelatinous side 

 to anij object that it strikes. He says : " The columella probably 

 begins to tear away at a point on the circumference of the line of 

 dehiscence, and the tear rapidly spreads. Through the aperture 

 thus produced water exudes, forming a drop which, as it grows, 

 increases the tear. This drop is moving with great velocity and 



1 At Guelph, at the second annual meeting of the Canadian Branch of the 

 American Phytopathological Society, Dec. 10, 1920. 



2 At Chicago, before the Physiological Section of the Botanical Society of 

 America, Dec. 28, 1920. 



3 At London, before the Linnean Society of London, June 16, 1921 {vide Proceed- 

 ings of the Linn. Soc, 1921, p. 63). 



* Loc. cit. 



5 C. T. Ingold, " The Sporangiophore of Pilobolus," The Neio Phytologist, 

 Vol. XXXI, 1932, pp. 58-63. 



