2 34 RESEARCHES ON FUNGI 



at the spore-hilum, i.e. at that part of the spore which bulges out- 

 wards just above the top of the sterigma (b). The drop grows visibly, 

 protruding laterally, and in about 20 seconds attains a diameter 

 equal to about one and one-half times the thickness of the spore (c). 

 Then, suddenly, the spore and the drop are shot away from the 

 sterigma together and disappear from view (d). The sterigma left 

 behind is apparently unchanged. The hyphal cell below it, with 

 which it is continuous, can often be seen at this stage to have a thin 

 layer of cytoplasm lining its cell-wall. This layer doubtless extends 

 into the sterigma. 



Violent discharge of the secondary conidia of Tilletia laevis was 

 found to take place in exactly the same manner as in T. tritici. 



Discussion of the Significance of Violent Spore-discharge in 

 Tilletia tritici. — The chief conclusions drawn by Buller and Vanter- 

 pool in respect to the theoretical significance of violent spore - 

 discharge were but briefly stated in their original communication. 1 

 They will now be more fully discussed. 



The asymmetrical development of a secondary conidium of 

 Tilletia tritici on a conical sterigma and the discharge of the 

 conidium with drop-excretion exactly resemble the processes of 

 development and discharge of a basidiospore as described by Buller 2 

 for the Hymenomycetes and by Dietel 3 and Buller 4 for the 

 Uredineae. This resemblance can have no other meaning than 

 that the sickle- shaped secondary conidia of Tilletia tritici are the true 

 basidiospores of this fungus. 



If the sickle-shaped so-called secondary conidia are the true 

 basidiospores of Tilletia tritici, what then are the long slender 

 primary conidia which hitherto have always been considered homo- 

 logous with basidiospores ? The answer is : sterigmata of a highly 

 specialised type. The evidence supporting this conclusion is as 

 follows : (1) the primary conidia are produced on the end of the 

 promycelium or basidium-body, (2) they are slenderly conical and 



1 A. H. R. Buller and T. C. Vanderpool, " Violent Spore -discharge in Tilletia 

 triticir Nature, Vol. CXVI, 1925, pp. 934-935. 



2 A. H. R. Buller, Researches on Fungi, Vol. II, 1922, pp. 4-18. 



3 P. Dietel, " t)ber die Abschleuderung der Sporidien bei den Uredineen," 

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



4 A. H. R. Buller, Researches on Fungi, Vol. Ill, 1924, pp. 497-519. 



