554 RESEARCHES ON FUNGI 



discharged their spores to a greater height when on a much thickened 

 petiole than when on a sUghtly thickened portion of a lamina. 



Finally, Zalewski observed that the aecidiospores are shot out 

 of their aecidia in dry air, although not so freely as in moist. 



Dr B. O. Dodge i of the Bureau of Plant Industry, Washington, 

 has recently confirmed Zalewski's results, for he has observed violent 

 aecidiospore-discharge in the following species : 



Gymnoconia peckiana on Rubus canadensis, 



Gijmnosporangiurn myricatum on 3hjrica cerifera, 

 Puccinia Podophylli on Podophyllum peltatum. 



The Podophyllum Rust shot its aecidiospores to a height of 

 1-1-5 cm. Dr. Dodge states that " the germ-pores of the aecidio- 

 spores of the Myrica and Podophyllum rusts are formed as a result 

 of a thickening of the spore-wall : small plugs are formed which 

 push into the spore opposite in such a way that, as the spore reaches 

 maturity and is pushed upwards, it comes into a critical position 

 where the resistance due to friction is not sufficient to balance the 

 elastic forces, whereupon the spore is suddenly released and shot 

 out to some distance. The spore-plug simply acts as an especially 

 good fulcrum." And Dr. Dodge adds : " I think that without 

 these plugs between the spores an aecidiospore would be shot out 

 some distance when released. The orange rust, Gymnoconia, dis- 

 charges its spores from the large caeomas with some force. There 

 are no pore-plugs, at least none of any size, formed in connection 

 with the germ-pores of this species." 



In the spring of 1924, whilst in England, I myself confirmed 

 Zalewski's results by observing violent aecidiospore-discharge in : 



Uromyces Poae on Ranunculus repens, 



Puccinia graminis on Berberis vulgaris, 



Puccinia jmlverulenta on Epilobium hirsidum, 



Puccinia Poarum on Tussilago Farfara.'^ 



1 B. 0. Dodge, ill lift. , , tt • •. -f 



2 Since this (!liapter was set up in type, Mr. J. H. Craigie of the University of 

 Minnesota has iuf.nMned mv i,i UtL tliat he has observed violent aecidiospore- 

 discharge in: Puccinia fraximUi, P. Clemutidis, P.lmpatientis, P. Grossulanae, 

 P. urticata, P. hieraciata, P. coronata, and P. graminis. 



