558 RESEARCHES ON FUNGI 



numerous compact rows of closely fitting many-sided aecidiospores 

 should hereafter be conceived of as correlated not merely with the 

 mode of production of the spores but also with the mechanism for 

 discharging them. In the past no one seems to have understood 

 this sufficiently. Hence the silence in our text-books in respect to 

 aecidial gunnery. There is every reason to believe that all typical 

 aecidia discharge their spores violently. 



The exact cause of aecidiospore-discharge is not fully clear 

 to me. Discharge only takes place when the aecidiospores are 

 sufficiently moist and therefore when the aecidiospores are turgid ; 

 and this suggests that the turgor of the ripe spores is an important 

 factor in the process. Where, at the end of a chain, two aecidio- 

 spores are attached together, the common wall is flat. Here, it 

 may well be, two opposing forces come into play : (1) the adhesion 

 of the two spores to one another, due, as we may suppose, to the 

 presence of a cementing intercalary-cell substance, and (2) the 

 pressure of the cell-contents of the spores, this pressure tending to 

 round off the spores and thus to make the walls cemented together 

 convex instead of flat. When the spores are ripening, we may 

 suppose that the adhesion of the two end spores to one another 

 becomes lessened or that their turgidity increases, until, at a 

 particular moment, the force of adhesion is overcome by the force 

 due to the cell-contents, the result being the sudden and violent 

 discharge of the terminal spore. However, each terminal spore 

 in a spore-chain is in contact not only with a subjacent spore at its 

 base, but with several other spores, belonging to other spore- 

 chains, round its lower half. This fact suggests that the same pair 

 of antagonistic forces which we have supposed comes into play 

 between the terminal and subterminal spores in a chain also comes 

 into play between a terminal spore and the spores by which it is 

 surrounded. Thus it may well be that the discharge of each spore 

 is due not merely to the overcoming of the force by which it adheres 

 to the subterminal spore by the force due to the turgor of itself 

 and the subterminal spore, but also due to the action of similar 

 antagonistic forces between itself and the spores surrounding its 

 lower half. 



The significance of violent aecidiospore-discharge is doubtless 



