THE PHENOMENA OF SPORE-DISCHARGE 499 



non-tremelloid Hymenomycetes).i Moreover, (3) the water-drop 

 excreted at the spore-hilum in the Uredineae is usually somewhat 

 larger and takes a few seconds longer to attain maximum size than 

 in the Hymenomycetes (10-40 seconds in the Uredineae as com- 

 pared with 5-10 seconds in the Hymenomycetes). 



So far as I am aware, Klebahn was the first to point out that 

 in the Rust Fungi the spores are violently shot into the air. He 

 says, in his work on Heteroecious Uredineae, published in 1904 : 

 "The sterigmata (Sporidientrager) appear to have the power to 

 shoot away the sporidia a certain, although a very short, distance, 

 so that it is not necessary for the wind first to break them off from 

 the places of their formation." 2 



In 1912, Coons,3 who employed the methods of observation 

 described in the first volume of this work, proved conclusively that 

 the sporidia of Gymnosporangium Juniperi-virginianae are violently 

 shot away from their sterigmata into the air in the same manner as 

 in Hymenomycetes. The horizontal distance of discharge was 

 found to be 0-26-0 -36 mm., and it was observed that the sterigma 

 and the spore are both turgid immediately after spore-discharge. 



In 1912, Dietel * published a paper on the discharge of sporidia 

 in the Uredineae, in which he brought to light a number of new 

 facts ; and, upon reading it, I at once perceived that his observa- 

 tions exactly resembled my own made when studying the discharge 

 of basidiospores in the Hymenomycetes. Dietel found that, when 

 a teleutospore-sorus of Puccinia (P. Malvacearum, P. Glechomatis, 

 P. aymularis), Coleosporium {C. Petasitidis, C. Cainpanulae, etc.), 

 or Cronartium (C. asclepiadeum) is cut out of a leaf and rested upon 

 a drop of water under a bell-jar, the sporidia settle at a distance 

 up to 0-6 mm. from the edge of the sorus, and that occasionally 

 in Coleosporium, which has large spores, the distance measures 

 0-85 mm. Dietel came to the conclusion that the spores, under 



^ These Researches, vol. ii, 1922, p. 169. 

 H. Klebahn, Die wirtswechselnden Rostpilze, Berlin, 1904, p. 30. 

 G. H. Coons, " Some Investigations of the Cedar Rust Fungus, Gymnospor- 

 angium Juniperi-virginianae," Annual Report No. 25, Nebraska Agricultural 

 Experiment Station, 1912, pp. 217-242. 



^ P. Dietel, " Uber die Abschleuderung der Sporidien bei den Uredineen." 

 Mycologisches Centralblatt, Bd. I, 1912, pp. 355-359. 



