500 RESEARCHES ON FUNGI 



normal conditions, can be shot about 0-6 mm. in a horizontal direc- 

 tion or about • 3 mm. upwards. However, he was not satisfied with 

 simply deducing the fact of violent spore-discharge from the position 

 of the fallen spores, but went further and observed the discharge of 

 spores from individual sterigmata. In Coleosporium PetasUidis, 

 Puccinia Arenariae, and Piicciriia Malvacearum, he discovered that, 

 just before spore-discharge, a tiny drop of water appears at the 

 top of each sterigma. His observations on the drop were as follows. 

 The drop at the top of the sterigma grows rapidly and in Coleo- 

 sporium attains a diameter of 9-10 /. in about 40 seconds. It often 

 appears to push the spore a little to one side. When the drop has 

 thus come into existence, the spore along with the drop is shot 

 away from the sterigma with violence. If one places a cover-glass 

 just above a teleutospore-sorus from which basidiospores are being 

 discharged, the spores are shot up against the cover-glass and stick 

 there along with the drop of water which each one has carried. 

 Normal sporidia-discharge in the Uredineae, as thus described by 

 Dietel so closely resembles normal basidiospore-discharge in the 

 Hymenomycetes, as described by myself, that doubtless the two 

 processes are identical. Dietel believed that a difference existed 

 between the Uredineae and the Hymenomycetes in that drops of 

 water were excreted by the former just before spore-discharge and 

 not bv the latter. My account of spore-discharge in the Hymeno- 

 mycetes had not then been published, so that it was left to me in 

 1915 to point out that this supposed difference does not exist and 

 that the phenomena accompanying the discharge of the basidiospores 

 in the Uredineae and the Hymenomtjcetes are identical} 



In 1917, Weimer,2 yging my beam-of-light method, like Coons, 

 observed the fall of the basidiospores of Gymnosporangium Juni- 

 peri-virginianae. In one experiment the discharge of the spores 

 continued from 6 p.m. until after 10 a.m. the next day. With the 

 microscope, Weimer observed that the basidiospore farthest from 



1 A. H. R. BuUer, " Die Erzeugung und Befreiung dei- Sporen bei Coprinus 

 sterquilinus," Jahrh. f. wiss. BoL, Bd. 56 (PfefEer-Festschrift), 1915, pp. 314-31o, 



^^^2 J. L. Weimer, "Three Cedar Rust Fungi. Their Life-histories and the 

 Diseases they Produce," Cornell University Agri. Exp. Station. Bull. 3J0, UU, 

 pp. 523-524. 



