HISTORY OF PILOBOLUS 



37 



yellow light, with a better reaction in blue light. Grantz ^ re- 

 peated Brefeld's experiments and confirmed them. According 

 to Kegel, 2 Pilobolus is positively hehotropic in white, blue, 

 yellow, and red hght at all the intensities and temperatures 

 employed. The con- 

 clusions of Brefeld, 

 Grantz, and Regel, as 

 we shall see, have 

 been substantially con- 

 firmed by the more 

 recent work of Miss 

 Parr. 



The first attempt 

 to express the photic 

 sensibility of plants in 

 quantitative terms was 

 made by Wiesner ^ 

 (1879) in his classic 

 work on hehotropism. 

 The next considerable 

 advance in this direc- 

 tion was made by 

 Blaauw* (1909), who 

 for the first time em- 

 ployed modern physi- 



FlG, 



13. — Pilobolus (Kleinii ?). A photomicrograph of 

 a group of fruit-bodies growing on dung in the 

 laboratory showing long slender stipes bearing 

 drops of mucilaginous fluid, beautifully sym- 

 metrical pear-shaped subsporangial swellings, 

 and jet-black di^c-shaped sporangia. The 

 diameter of each subsporangial swelling consider- 

 ably exceeds that of the sporangium which crowns 

 it. Owing to the heliotropic curvature of the 

 stipes, the sporangia all faced the source of 

 strongest light. Photographed by B. O. Dodge. 

 , , , -1^, Magnification, about 3 -5. 



cal methods. Blaauw 



investigated the heliotropic response of Phycomyces nitens. 



Miss RosaUe Parr ^ (1918), reahsing that the chief reason for the 



1 F. Grantz, Ueber den Einfluss des Lichtes avf die Entwicklung einiger Pike, 

 Inaug. Diss., Leipzig, 1898 (cited from Allen and Jolivette). 



2 K. Regel, " Ueber die Einwirkung des Lichtes auf Pilze," Sitzungsber. d. Bat. 

 Sect. d. St. Petersburger Naturf.-Oes., Jan., 1881 (in Russian) ; summary in Bot. 

 Zeit., 1882, p. 29 (cited froin Allen and Jolivette). 



^ J. Wiesner, " Die heliotropischen Erscheinungen ini Pflanzenreiche," Denk- 

 schriften d. K.-k. Acad. Wien, Vol. XXXIX, 1879. 



* A. H. Blaauw, " Die Perception des Lichtes," Rec. d. Trav. bot. neerl. Vol. V, 

 1909. 



^ Rosalie Parr, " The Response of Pilobolus to Light," Annals of Botany, 

 Vol. XXXII, 1918, pp. 177-205. 



