THE TRANSLOCATION OF PROTOPLASM 133 



convex body with a diameter of about 1 /a. Its more convex side 

 bulges forward from the pore into the lumen of the dead cell (Fig. 68). 

 The substance of which a plug is composed appears homogeneous, 

 colourless, and highly refractive, and may well be nothing more 

 than a coagulum of protoplasmic origin. We may suppose that the 

 death and disorganisation of the protoplasm of a cell instantaneously 

 causes those parts of the living protoplasm of the two adjacent 

 cells which happen to be in the pores of the two septa and are 

 beginning to press through them to solidify and thus form plugs. 



Ordinarily, in a living hypha, the pressure on the two sides of 

 a septum is equal or nearly so and the septum is plane. The bulging 

 forward of a septum when one of the cells adjacent to it is killed is 

 due to the turgidity of the living cell. As is well known, a similar 

 bulging of septa takes place in a Spirogyra filament whenever one 

 of the cells in the chain ceases to live. 



Formation of Pore Plugs in Old Mycelia when Individual Cells 

 Die. — When spores of Pyronema confluens are sown in a hanging drop 

 of dung-agar, the mycelium resulting soon spreads throughout the 

 drop. At first all the numerous cells of which it is composed are 

 living ; during the next day or two certain hyphae lose their proto- 

 plasmic contents and die ; and, in the course of two or three weeks, 

 certain cells of the larger main hyphae die and thus the living parts 

 of the hyphae become separated from one another. As a cell in the 

 middle of a living hypha dies, its septa become pressed into it by 

 the adjacent living cells and the septal pores become plugged just 

 as when a cell is killed suddenly on being injured with a needle. 

 We may therefore conclude that, under natural conditions, the 

 plugging of the pores of septa which divide living from dead cells 

 is a normal phenomenon. 



Pore Plugs in Other Fungi. — In all probability pore plugs are 

 formed between dead and living cells in the mycelium of Discomy- 

 cetes in general. It is true that they were not recorded as being 

 present in Lasiobolus pulcherrimus , Ascojihanus carneus, and Asco- 

 bolus magnificus by Woronin, 1 Ternetz, 2 and Dodge 3 respectively, 



1 M. Woronin, loc. cit. 2 C. Ternetz, loc. cit. 



3 B. 0. Dodge, " The Life History of Ascobolus magnificus,'" Mycologia, Vol. XII, 

 1920, pp. 115-134. 



